The duty of candour in UK judicial review

Anyone involved in a judicial review case must understand this fundamental duty, and the steps needed to comply with it, as non-compliance can lead to serious consequences.

What is the duty of candour?

The duty of candour requires all parties to ensure that all information, material and explanations relevant to the case are put before the court. It is a distinct and separate duty from the disclosure duties which apply in most civil proceedings.

• Read more: our guide to UK judicial review

The distinction ultimately derives from the different relationship between the defendant and the court in judicial review cases. In judicial review, those exercising public functions are not engaged in ordinary litigation, trying to defend their own private interests. Rather, the common purpose of all parties and the court in a judicial review should be to protect the public interest in the lawful exercise of public functions.

As a result of this fundamental difference, it is often the case that more is required of parties to comply with the duty of candour than would be required under the disclosure duty in ordinary civil litigation.

The duty of candour derives from the common law, and there is no single place where it is codified or embodied, having been articulated through a large body of case law. In addition to these cases, the key sources of guidance on the nature and extent of the duty are to be found in the Administrative Court Judicial Review Guide (248-page / 1.85MB PDF) and the Treasury Solicitor's Guidance on Discharging the Duty of Candour and Disclosure in Judicial Review Proceedings (27-page / 230KB PDF).

Who does the duty of candour apply to?

The duty applies to all parties to judicial review proceedings. It is particularly important for defendants – so public authorities and others exercising a public law function – who will generally hold most information and documents relevant to the claim. But it also applies to claimants and interested parties, as regards relevant information or documents they hold.

What is required to comply with the duty?

In practice, the duty of candour typically requires a mix of explanation through witness statements and the provision of key documents.

What is required to comply with the duty in each case ultimately flows from the fundamental question of what is necessary to ensure that all relevant information and all material facts relevant to the claim are put before the court. Some key principles that can be distilled from the cases are:

• Disclosing lots of documents to an opponent is often unnecessary and inappropriate. The duty of candour is “information-based” and is primarily concerned with ensuring all relevant information and facts are put before the court.
• However, where a party relies on a document, and the document is significant to the decision under challenge, it will be good practice to disclose that document rather than merely summarise it, because the document is the best evidence of what it says.
• Having said this, provision of contemporaneous documents may not be enough on its own to comply with the duty in some cases. The duty also requires that relevant facts be identified in witness statement evidence, insofar as not apparent from disclosed contemporaneous documents.
• Provision of information under the duty of candour must not be selective but must include the unwelcome along with the helpful. As put in one case, it is incumbent upon the public authority to identify “the good, the bad and the ugly”.
• The duty extends to documents and information held by the defendant that may give rise to further grounds of challenge by the claimant.

For claimants, compliance with the duty may require the disclosure of matters, including material facts and known impediments, that could potentially undermine their claim. Claimants must also disclose materials acknowledging any issue of delay in bringing the claim, since judicial review claims must be brought promptly and, in any event, within three months after the grounds for making the claim first arose.

Does the duty require sensitive documents to be disclosed?

Information must be disclosed if it is relevant. Further, documents considered by government departments or other public bodies to be sensitive or embarrassing must still be disclosed if relevant.

The courts’ approach to the disclosure of sensitive documents was neatly illustrated in two 2024 judicial reviews concerning the government’s climate change policy. The government’s defence to the first case rested on the argument that there were no risks to the delivery of the planned actions. However, it was required to disclose its own internal risk assessment documents identifying and quantifying those risks, thus undermining its defence.

In the second case, the claimants pressed for disclosure of the internal briefing and advice given by officials to the minister, which led to the decision that was the subject of the challenge. In this case the court considered the internal advice was not relevant and did not need to be disclosed, because the challenge would stand or fall on what was set out in the minister’s published decision letter setting out the reasons for the decision.

However, there are also limited, narrowly defined circumstances in which parties are permitted to redact certain information within a document:

• legal professional privilege;
• a statutory restriction on disclosure; or
• public interest immunity.

At what stage does the duty of candour apply?

The duty applies at every stage of judicial review proceedings, and continues to apply until their resolution.

What the duty of candour requires of parties will depend on the stage of the proceedings. For defendants, what is required to discharge the duty at the substantive stage will be more extensive than what is required before permission has been granted.

Although the duty of candour does not apply before proceedings are issued, similar principles apply under the judicial review pre-action protocol as regards the expectation that parties should disclose to one another information that is relevant to their pre-action correspondence.

At the permission stage of a judicial review after proceedings have been issued, the duty requires the parties to disclose sufficient information to enable the court to decide if there is an arguable case to which it should grant permission to proceed.

At the substantive stage of a case after permission is granted, the duty requires a defendant to identify any relevant facts and the reasoning underlying the measure that is being challenged.

Practical steps to support compliance

In practice, compliance with the duty of candour is often more burdensome for Defendants, as they will hold most of the information and documents relevant to their decision being challenged in the judicial review. The Treasury Solicitor's Guidance recommends a number of practical steps that a government department or other public body should take to ensure compliance with the duty, which include:

• preserve documents and maintain records as soon as it becomes aware that proceedings are likely;
• conduct thorough and transparent searches for documents, and consider whether it needs to obtain material information or documents from any non-parties to the proceedings;
• appoint a litigation case-handler who can oversee the disclosure exercise and have overall responsibility for compliance with the duty of candour.

How is the duty of candour enforced by the courts?

A failure to comply with the duty of candour can have very serious consequences for parties if the court considers they have withheld relevant information or documents. Options open to the court include:

• drawing inferences against the offending party on points which remain obscure;
• taking into account a lack of candour in deciding whether to grant permission;
• granting an order requiring disclosure of specified documents;
• making an order for costs against the party;
• a determined case being reopened;
• reporting legal professionals to the regulator for disciplinary action;
• proceedings for contempt of court against parties or individuals in persistent breach.