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UK life sciences research delivers vital benefits for human and animal health, the environment and the economy. Some of this research requires the use of animals to achieve essential scientific outcomes, and it is our responsibility to ensure that those animals are afforded the highest standards of protection. Equally, it is critical to maintain public confidence that, where animals are used, their use is fully justified and there is no viable alternative.
The Animals in Science Regulation Unit (ASRU) plays a central role in safeguarding animal welfare in research and testing. We ensure animals are used only when absolutely necessary, and only to the extent required to meet research objectives. Harms must be minimised, and the principles of the 3Rs (Replacement, Reduction and Refinement) are embedded in every aspect of our regulatory approach. Our work is underpinned by the Animals (Scientific Procedures) Act 1986 (ASPA), which sets a robust legal framework for ethical and responsible science.
Regulation of animal testing in the UK is essential to protect animals from unnecessary suffering, ensure that testing occurs only when no alternatives exist, and promote the development of innovative non‑animal methods. These measures uphold the ethical treatment of animals while enabling research that advances medicine and science, with the long‑term goal of replacing animal use entirely.
Throughout 2024, ASRU has continued to strengthen its regulatory delivery through a transformational reform programme designed to enhance compliance and ethical standards, while supporting scientific innovation.
We have initiated an organisational restructure that will continue into 2025, ensuring our regulatory practices remain fit for purpose and responsive to future challenges.
Our reform programme will deliver stronger protections for animals, reinforce compliance with ASPA, and foster collaboration with the regulated sector to achieve meaningful improvements. We remain committed to driving forward these reforms, maintaining the highest standards of animal welfare, and supporting world‑class science that benefits society.
The purpose of ASRU is to protect animals used in science by maintaining compliance with the Animals (Scientific Procedures) Act 1986 (ASPA).
Through its regulatory role, ASRU ensures that scientific work involving animals is conducted responsibly, legally, and with the highest regard for animals.
ASRU regulates the use of animals in science according to ASPA. This is the UK law passed by Parliament that governs how and under what circumstances animals may be used in science.
ASPA sets strict conditions on which types of animals can be used, the types of procedures permitted, and the ethical standards researchers must follow. At the heart of ASPA is the requirement to:
ASRU is part of the Home Office and is responsible for the administration and enforcement of ASPA in England, Scotland and Wales. ASRU’s activities include:
ASRU delivers these responsibilities through its Licensing and Compliance Assurance functions, supported by additional functions which deliver business support and oversee processes and standards. As of 31 December 2024, 33.8 full‑time equivalent (FTE) employees worked in ASRU.
ASRU inspectors evaluate licence applications against the requirements of ASPA and use a harm‑benefit analysis process to determine whether a project licence should be authorised.
ASPA has a three‑tiered licensing system (a licence is required for the person, the project and the place):
Those breeding and/or supplying the species of animal listed in ASPA Schedule 2 must also hold PEL.
The conduct of regulated procedures may be authorised at places other than licensed establishments (POLEs) when the nature of the work makes this necessary, and these places will be specifically identified in the relevant PPLs.
The principles of replacement, reduction and refinement (the 3Rs) as set out by the National Centre for the Replacement, Reduction and Refinement (NC3Rs).
Replacement is the principle that, wherever possible, a scientifically satisfactory method or testing strategy not entailing the use of protected animals must be used instead of a regulated procedure. Replacement accelerates the development and use of predictive and robust models and tools, based on the latest science and technologies, to replace the use of animals in addressing important research questions where they would otherwise have been used.
Reduction is the principle that, wherever a programme of work involving the use of protected animals is carried out, the number of protected animals used must be reduced to a minimum without compromising the objectives of the programme. On occasions, it may be necessary to use a greater number of animals than the absolute minimum scientifically justifiable if each individual animal will suffer less because of the greater number being used. The principle of reduction should apply to methods of breeding protected animals, as well as their use in procedures. Reduction results in appropriately designed and analysed animal experiments that are robust and reproducible and add to the knowledge base.
Refinement is the principle that, wherever a programme of work involving the use of protected animals is carried out (after rigorously applying the principles of replacement), the regulated procedures applied to those animals must be refined to eliminate or reduce to the minimum any possible pain, suffering, distress or lasting harm. Refinement and reduction must be considered in balance. Refinement applies to the methods of breeding, accommodation and care of protected animals as well as the methods used in procedures. Refinement advances laboratory animal welfare by applying the latest in vivo technologies – techniques conducted within a whole, living organism – to minimise pain, suffering and distress, and to improve understanding of how welfare impacts scientific outcomes.
Personal licence holders’ responsibilities for the 3Rs:
Project licence holders’ responsibilities for the 3Rs:
Establishment licence holders’ responsibilities for the 3Rs:
In 2024, the licensing function’s work included:
As of 31 December 2024, the licensing function of ASRU comprised the following FTE personnel:
Note: FTE data has been rounded to one decimal place for reporting purposes.
The Compliance Assurance function is responsible for delivering a comprehensive suite of oversight and assurance activities to ensure that licence holders comply with ASPA and their specific licence conditions. This function plays a critical role in maintaining the integrity of the regulatory framework and upholding public confidence in the system.
In 2024, the Compliance Assurance function’s key activities included:
As of 31 December 2024, the Compliance Assurance function within ASRU comprised of the following personnel:
ASRU’s Business Support function provides business support to all ASRU colleagues, including managers and leaders.
In 2024, the Business Support function’s work included:
As of 31 December 2024, the Business Support function of ASRU comprised 2.5 FTE personnel.
Note: FTE data has been rounded to one decimal place for reporting purposes.
ASRU’s Process and Standards function oversees the development, refinement and implementation of procedural documents in ASRU.
In 2024, the Process and Standards function work included:
As of 31 December 2024, the Processes and Standards function of ASRU comprised 2 FTE personnel.
In 2020, a programme of transformational regulatory change was initiated to improve the performance of ASRU. The change programme was targeted at delivering alignment of the Regulator with the following expectations:
In July 2021, ASRU changed its regulatory operating model to align ways of working with regulatory practices and modern regulatory systems. In doing so, ASRU separated Compliance Assurance and Licensing functions, with inspectors no longer assigned to specific establishments.
In 2022, the regulatory reform programme paused to gather feedback from establishments and the wider sector, and consolidate new processes and establish the new Animals in Science Regulation Policy Unit in the Home Office. The Policy Unit is a separate entity from ASRU and advises ministers on policy relating to regulating the use of animals in science, principally under ASPA.
In 2023, the regulatory reform programme was re‑initiated, and ASRU undertook a comprehensive review of its operating model and organisational design. This exercise identified opportunities for improvement to strengthen regulatory delivery. Key considerations included the robustness, proportionality and efficiency of ASRU’s Licensing, Compliance Assurance and Guidance functions, as well as its culture and broader internal systems.
The new operating model and organisational design were developed to provide ASRU with the capabilities, structure and expertise required for effective operation and efficient delivery of its statutory responsibilities.
In 2024, ASRU continued to design and implement organisational changes, aligned with its mission to strengthen animal protections and support the life sciences sector through effective and proportionate regulation. Preparations were made to launch the finalised operating model and new organisational structure in 2025.
The new operating model incorporates a strengthened strategic centre, enhanced data analysis capabilities to enable a more evidence‑based approach, and increased expertise in regulatory and quality management functions. It also introduces a broader and more diverse range of skills, strengthening ASRU’s capabilities across standards and guidance, quality assurance, data analysis and regulatory practice. This broader multidisciplinary input strengthens regulatory expertise, ensuring that audits and other key activities benefit from diverse perspectives.
The reform programme continued throughout 2025, with further improvements to ASRU planned and regular stakeholder engagement to support transparency and effective regulatory delivery.
Continuous improvement is at the heart of ASRU’s regulatory reform programme, to ensure that changes are not only implemented, but refined over time to deliver robust, proportionate and efficient regulation.
ASRU’s principles, processes and standards used in licence assessment continue to align with ASPA requirements.
The three‑tier licensing system provides a framework for authorising research using animals, ensuring that animal research and testing is only undertaken:
ASRU administers and issues the following types of licences:
Licence applications are assessed by inspectors in the order they are submitted through ASPeL.
We prioritise licence applications using timelines aligned within the statutory timelines defined in ASPA. Timelines to grant licences can vary, as they are based on the complexity of the application and level of incoming applications to the regulator.
All days referenced are working days:
As of 31 December 2024, ASRU licensed and regulated 134 establishments.
These establishments include universities, pharmaceutical companies and contract research laboratories. As of 31 December 2024, there were 2,315 active PPLs and 13,311 active PILs.
In 2024, 2 PELs were granted, 3 were revoked, and 3,440 amendments were made. These amendments included changes to areas approved for animal holding/procedures, Named Persons and administrative information.
In 2024, 472 new PPLs were granted and 905 PPL amendments were made. This is a slight increase in the number of new PPLs granted compared to 2023 (460 PPLs granted).
During 2024, 2,164 new PILs were granted and 738 PIL amendments were made.
In 2019, ASRU rolled out ASPeL, a refreshed digital e‑licensing system, to improve consistency, efficiency and compliance.
The ASPeL system ensures that PIL holders and Named Persons can easily access the information they need to do their work, reducing the risk of inadvertent non‑compliance.
Applicants can track the progress of their applications and any mandatory actions, such as when a PIL is due for review.
ASRU recognises that the new project application forms can be further improved and has committed to ongoing development of ASPeL to ensure it meets both internal and external user needs while maintaining robust animal protections. Improvements to ASPeL include:
ASC is an independent, non‑departmental public body convened under sections 19 and 20 of ASPA. ASC provides independent, balanced and objective advice to the Secretary of State on issues relating to the use of animals in science. At all times, ASC must consider both the legitimate requirements of science and industry and protecting animals from avoidable suffering and unnecessary use in scientific procedures.
Further information about ASC is available on its dedicated website.
ASC also advises on specific categories of PPL applications, including those applications that seek authority for:
ASRU’s compliance policy focuses on the delivery of a proportionate, consistent and outcome‑based approach to incidents of non‑compliance. Every establishment licensed under the Animals (Scientific Procedures) Act 1986 (ASPA) has a Named Person Responsible for Compliance (NPRC). This individual ensures compliance with the conditions placed on their establishment licence. A good culture of compliance at an establishment reflects evidence of effective governance over the use of animals in science. The NPRC must maintain robust systems and frameworks that support and assist all licensees to comply with their licence conditions.
Establishments notify ASRU of any incidents where there has been a potential breach of ASPA or a licence condition (which also includes the Code of Practice for the Housing and Care of Animals Bred, Supplied or Used for Scientific Purposes (Code of Practice).
Self‑reporting indicates that an establishment is making efforts to ensure compliance.
It demonstrates that role holders are aware of their responsibilities and are committed to building a compliant culture. ASRU expects self‑reporting to be embedded within good governance frameworks and that employees are aware of the process for raising concerns within their establishment. This is set out in ASRU’s published compliance policy Guidance on the operation of the Animals (Scientific Procedures) Act 1986 (ASPA) – GOV.UK
ASRU may identify potential breaches when auditing an establishment. When this occurs, the establishment is notified in the audit report that a potential non‑compliance has been identified and may be investigated.
ASRU takes all reports of potential non‑compliance seriously. An inspector will gather sufficient information to determine whether there is a case that merits further investigation. If the ASRU Enforcement Team determines that there is sufficient evidence for a breach, it will issue a suitable and proportionate remedy. The aim of this remedy is to prevent a recurrence of similar breaches.
Licensees and the establishment are notified in writing by ASRU when a non‑compliance investigation is being conducted and are given an opportunity to provide any information that they wish to be considered before ASRU takes a decision regarding the appropriate remedy.
There is also the opportunity for appeal against some types of remedy, which the licence holder will be notified of at the time the remedy is issued. Complex or serious cases may take some time to resolve. In rare cases, ASRU may take a view that an offence has been committed that is sufficiently serious to merit referral for prosecution.
ASRU considers cases individually and applies the most appropriate remedy for the severity of the non‑compliance and the aggravating and mitigating circumstances. ASRU takes the resulting measures and sanctions to deter or prevent a recurrence.
Factors considered when determining suitable remedy include:
The range of remedies available, as set out in the published compliance policy, benchmark and help to determine the outcome associated with each breach. These are briefly outlined below.
For a minor breach, an inspector will advise on what provision was breached and what is expected in the future to prevent a recurrence. A minor breach is one where:
Where provision of inspector advice is not considered sufficient, most cases of non-compliance are dealt with by a letter from ASRU, with or without a variation of the relevant licence(s). Where a breach has been committed by a licensee, a Letter of Reprimand is sent. Where a non‑licensee has contributed significantly to the breach, a Letter of Censure may be sent.
Letters note the breach(es) that have occurred and summarise the evidence for those breaches. These letters are formal records of non‑compliance and may be used as evidence should there be a further breach within 5 years. All letters are also sent to Home Office Liaison Contacts (HOLCs), so that local practices and processes can be reviewed as appropriate.
Re‑training is required where a licensee has demonstrated that they do not have the expected level of knowledge of their legal responsibilities or to undertake procedures.
Where action is required to improve weaknesses identified by a breach, including poor record keeping, a report may be required to monitor progress. Reports are also useful for formally monitoring enhanced animal welfare, implementing refinements or improving scientific outcomes.
Suspensions are appropriate where there is a risk to animal welfare and significant, urgent action is required to protect it. Where a breach has been identified, ASRU may suspend the licence as a sanction. It may also suspend licences when there are urgent animal welfare concerns. When a suspension is required, ASRU must ensure that the suspension itself does not result in any further adverse impact on animal welfare.
ASRU will issue a Compliance Notice where it requires action to be taken to prevent further non‑compliance. Such a notice will specify:
The Compliance Notice will set out the consequences of failing to comply. In this eventuality, ASRU may sanction the licence holder with a suspension, variation or revocation of their licence.
This type of remedy is particularly effective where specific actions are required to assure ASRU that the breach will not recur. ASRU usually specifies a timeframe for the actions to be completed; if not completed by that timeframe, it may sanction further, such as with the suspension, revocation or variation of the licence.
ASRU will only revoke licences issued under ASPA in the most serious cases. It is appropriate where a licensee has shown a disregard for the controls of the ASPA and has caused avoidable suffering to animals. It may also be appropriate where significant avoidable suffering has been caused through negligence or ignorance, or where the licensee otherwise appears to be unsuitable for the role. ASRU has a duty to ensure that the welfare of animals is not adversely affected by the revocation of a licence.
Extremely serious cases of non‑compliance are referred to the prosecuting authorities to judge whether it would be in the public interest to prosecute. Prosecution could lead to a fine or imprisonment.
In 2024, 146 cases of non‑compliance, in 45 different establishments, were confirmed and finalised. Of these, 63 (43%) were related to failing to provide adequate care (including food, water and suitable facilities) while the other 83 (57%) were related to failing to have or adhere to licence authorities. See Figure 1, below.
Note: The graph shows the percentage of cases by category of non‑compliance. The number of cases in each category is shown at the end of each bar in brackets.
In 2024, 101 (69%) of the cases closed as confirmed non‑compliances were self‑reported by establishments as potential non‑compliances; 36 (25%) were identified by ASRU from PPL Standard Condition 18 reports, 4 (3%) during an audit, 3 (2%) by the Licensing Team and 1 case each by the Regulatory Advice Team and via the Return of Procedures process (<1% each).
In 2024, of the 146 cases of non‑compliance, animal numbers were reported in 143 cases; animal numbers were not relevant for 3 cases related to administrative errors or facility‑wide issues that did not impact animals directly.
These 143 cases involved 22,204 animals.
The number of animals reported in the 143 cases, by animal type, is shown in Table 1.
There was one case that involved a larger number of animals – 13,952 mice and 1,625 rats. There was a fault with the environmental control systems at the animal facility, which led to temperature and humidity fluctuations outside the Code of Practice parameters. Five animals experienced adverse welfare as a result of this non‑compliance.
An animal is assessed as experiencing an adverse welfare outcome as the result of a non‑compliance if they experienced greater than short‑term mild pain, suffering or distress, taking into consideration:
Animals that were bred in excess of the authorised numbers, but were required to achieve the scientific objectives, were not considered as having experienced an adverse welfare outcome providing licence authorities and controls were adhered to.
In 2024, 189 animals experienced adverse welfare outcomes because of non‑compliance (Table 2). This is a reduction from the number of animals that experienced adverse welfare outcomes in 2023, which was 553.
Table 2: Number of animals with adverse outcomes, 2024
It should be noted that in a single case of non‑compliance, there can be several different remedies applied to a variety of individuals. Therefore, the number of remedies is not the same as the number of cases.
Note: The number of remedies issued is shown in brackets.
Note: The number of remedies issued is shown in brackets.
There were 110 cases (75%) for which the sole remedy was inspector advice. Summaries of all the non‑compliance cases closed in 2024 are in Annex A.
Note: The number of cases in each category is shown at the end of each bar.
In 2024, 68 (47%) of the 146 cases involved failure to comply with PPL authorities.
The main root causes of these types of non‑compliances were:
The following recommendations are made to reduce the risk of not complying with PPL authorities:
In 2024, there were 54 cases (37%) of inadequate care. Recommendations to prevent this type of non‑compliance are:
Failing to provide sufficient food and/or water to animals, as part of basic husbandry and care, is unacceptable. Establishments must always have robust procedures in place to ensure the adequate provision of food and water to animals kept under the provisions of ASPA.
In 2024, of the 146 cases of non‑compliance, 9 (6%) involved failure to provide adequate food and/or water.
Cases in which there was a welfare impact occurred due to the failure of establishment processes to ensure that the necessary daily checks were performed adequately. When performed competently, the absence of food and water would be detected prior to adverse welfare outcomes occurring.
Recommendations to prevent this type of noncompliance are:
the presence of food and water after any activities involving animals
Section 3(a) of ASPA requires that no person shall apply a regulated procedure as part of an authorised project to an animal unless they hold a relevant PIL.
In 2024, 11(8%) cases were recorded where the breach was either failing to hold a PIL or to have the relevant authorities on their PIL to conduct the regulated procedures undertaken.
Recommendations to prevent this type of non‑compliance are:
In 2024, 2 (1%) cases were recorded where regulated procedures had been performed in a room not authorised on the PEL, or an animal had been kept in a room not authorised for overnight holding.
Recommendations to prevent this type of non‑compliance are:
This category was added to the 2022 annual report to accurately capture the number of non‑compliance cases that cannot be placed into the five previously used categories.
In 2024 there 2 (1%) cases recorded where there were failures to adhere to licence conditions that mandate record keeping, re‑homing and security.
All project licences are subject to a set of Standard Conditions. Standard Condition 18 requires that the PPL holder notifies ASRU as soon as possible if constraints on the severity limits, or observance of other controls described in the licence, have been breached or are likely to have been breached.
Licence holders are required to submit reports under Standard Condition 18 as a requirement of ASPA, ensuring that unexpected events are reported to ASRU so that advice can be provided or compliance action taken.
Notification to ASRU under PPL Standard Condition 18 relates to breaches or likely breaches of either severity limits or any other controls set in the licence. Notification provides an important opportunity for the licence holder, the establishment and ASRU to review whether any changes need to be made to licence authorities and is an important source of data for ASRU compliance assurance. Notification under PPL Standard Condition 18 is required for compliance and is not the same as reporting potential non‑compliance.
In 2024, ASRU received 2,466 Standard Condition 18 reports from establishments.
An audit is a process that verifies conformance to standards through a review of objective evidence. Audits provide assurance to ministers and the public that there are systems in place to ensure care of animals and that the experiments undertaken comply with ASPA requirements and the relevant conditions specified in licences. ASRU advises duty holders on how to comply with ASPA requirements and will enforce non-compliances.
ASRU audits establishments licensed to breed or supply animals, or to undertake regulated procedures on animals under ASPA in England, Scotland and Wales.
The purpose of ASRU's audit activity is to assess compliance against ASPA and associated licence conditions, and to objectively measure the risk of non‑compliance within the establishment by assessing the robustness of governance systems.
ASRU undertakes audits for the following purposes:
Audit is primarily supportive and aims to recognise areas where systems are strong to maintain compliance, as well as identifying areas where improvements could be made. Although non‑compliance may be detected during an audit, it is not primarily an enforcement activity but a monitoring and educational activity.
The new audit approach was first rolled out in 2021 to 2022 and has continued in 2024 to replace the previous old‑style inspection programme.
ASRU's audit activity is risk‑based, taking into consideration the factors specified in section 18 (2C) of ASPA, which are:
As of 31 December 2024, ASRU had audited 68 establishments. This comprised 66 facilities audits, 2 for‑cause audits and no dual‑purpose audits. Of these audits, 10 were unannounced to the establishments.
Five audits included in the 66 facilities audits above were carried out by remote inspection and interview for operational reasons, such as work at POLEs that may not have physical facilities.
As part of regulatory reform the audit programme has undergone a review which will continue into 2025, with further changes anticipated through 2026 and into 2027.
Following an audit, an establishment receives a report detailing the findings of the audit, including timescales for confirming to ASRU that any required follow‑up action has been completed. This allows any necessary action to be undertaken by the establishment and ASRU to monitor its completion in a timely manner.
ASRU's establishment risk management process comprises a review of the national risk profile and local establishment factors.
Evaluation of risk includes:
ASRU takes these factors into account when planning audit activity.
ASRU periodically receives allegations about potential breaches of ASPA. These are taken seriously and, where sufficient information is provided, they are followed up by the most appropriate means, which may include initiating a for‑cause audit. Where it appears there may have been a lack of compliance with ASPA, these are investigated in accordance with ASRU's non‑compliance policy.
Notes:
1. This figure has been corrected, it was previously reported as a positive variance £356,094.
2. This figure has been corrected, it previously reported as (£86,528).
Increases in licence fees are necessary to ensure that fee income continues to cover all expenditure incurred in delivering the ASRU service.
Note:
1. From 2018, fees are charged from 6 April each year, which is the common commencement date and is in line with practices in other government departments. Prior to 2018, fees were charged from 1 April.
Invoices are raised in arrears, so the income for the year ending March is collected in the following year.
Table 5: Summary of expenditure by budgeting years ending March 2021 to 2025
Stakeholder engagement is a critical enabler of effective regulation, policy implementation and service delivery. ASRU's engagement with the regulated sector and other key stakeholders serves multiple strategic and operational purposes:
ASRU's engagement with the regulated sector plays a critical role in delivering its regulatory responsibilities. Engagement is structured around 3 tiers of requirements:
Through these interactions, ASRU can:
Stakeholder meetings continue to play a vital role in ASRU's reform programme, helping to strengthen transparency, improve regulatory delivery, and support compliance with ASPA. These engagements provide valuable feedback, foster trust, and ensure the regulated sector remains informed and involved in shaping improvements.
In 2024, ASRU met with the Home Office Liaison, Training and Information Forum (HOLTIF) three times, providing a platform for the regulated sector to receive updates on key regulatory developments and contribute feedback.
ASRU also met with the Establishment Licence Holders Committee three times in 2023.
These meetings included an update on the reform programme and discussions of strategic and operational matters.
In 2024, ASRU published:
ASRU supports the Animals in Science Regulation Policy Unit to respond to Freedom of Information Act 2000 (FOI) requests or correspondence from the public on issues related to regulating animals in science.
In 2024, the Policy Unit handled 71 FOI requests and 110 items of ministerial correspondence, including other related communications.
The requests and correspondence above were concerned with a breadth of issues. Among these, the main topics of interest were:
Table A4: Failure to have appropriate personal licence (PIL) authority
Table A5: Unauthorised location: Performing procedures or keeping animals in area not specified on PEL
Table B2: Inspectorate staff years, ending March 2011 to 2024
Total number staff at year end Average FTEs through year
Note: FTE = full‑time equivalent averaged across the year
