Judicial review (JR) is the jurisdiction of the High Court (Administrative Court) to supervise the exercise of public power. It is one of the most important mechanisms in the English legal system for holding government and public bodies to account. But it is widely misunderstood — many people assume JR is a way to challenge a decision you disagree with on its merits. It is not. JR asks whether a decision was lawful, not whether it was right. For the formal definition, see the judicial review glossary entry.
Who can be judicially reviewed?
JR lies only against "public bodies" or bodies exercising "public functions." This includes: central government departments and ministers; local authorities; the police and Crown Prosecution Service; planning authorities; NHS trusts and clinical commissioning bodies; regulatory authorities such as Ofcom, the FCA, and the CQC; universities and examination boards (in relation to their public functions); and the courts and tribunals themselves (in limited circumstances). Private companies acting under statutory powers — a utility company exercising compulsory purchase powers, for example — may also be subject to JR in relation to those public functions. Pure private law disputes (a contract dispute between two private parties) cannot be judicially reviewed — they must be resolved in the ordinary civil courts.
The grounds of judicial review
The classic statement of grounds comes from Lord Diplock in Council of Civil Service Unions v Minister for the Civil Service [1985] AC 374 (the GCHQ case): illegality, irrationality, and procedural impropriety. These have been elaborated since:
Illegality: The decision-maker must correctly understand the law and act within the powers granted by Parliament. This includes: acting outside the statutory powers entirely (ultra vires); using powers for an improper purpose; failing to exercise a statutory discretion by fettering it with a rigid policy; and delegating to the wrong person. Under the Human Rights Act 1998, it is also unlawful for a public authority to act incompatibly with a Convention right.
Irrationality (Wednesbury unreasonableness): From Associated Provincial Picture Houses Ltd v Wednesbury Corporation [1948] 1 KB 223. A decision is unlawful if it is so unreasonable that no reasonable decision-maker could have reached it. This is a high bar — the court does not substitute its own view of what was reasonable. For decisions that engage fundamental rights, a heightened rationality standard ("anxious scrutiny" or proportionality) applies.
Procedural unfairness: The decision-maker must follow a fair procedure: the right to a fair hearing (audi alteram partem); the right not to be judged by someone with a conflict of interest (nemo iudex in causa sua); the duty to give adequate reasons; and the duty to consult where there is a legitimate expectation of being consulted. Where a public body has made a promise or created an expectation, it may be bound by that expectation under the doctrine of legitimate expectation.
The permission stage
JR claims must be brought promptly and in any event within three months of the date of the decision (shorter periods apply in planning (six weeks) and procurement cases). Claims are filed on Form N461 and served on the defendant public body. The court first considers whether to grant permission to proceed, usually on the papers (without a hearing). The test is whether the claim is "arguable" — whether there is a real prospect of success. If permission is refused, you can renew the application orally. The permission stage filters out obviously unmeritorious or untimely claims before the defendant has to engage fully. This is designed to protect public bodies from having to respond to every speculative challenge.
What happens if you win?
If the court finds the decision was unlawful, it has a range of remedies, all of which are discretionary: a quashing order (setting aside the unlawful decision — the most common remedy); a mandatory order (requiring the public body to perform a duty it has unlawfully failed to perform); a prohibiting order (preventing the public body from taking the unlawful action); a declaration (declaring the law or the rights of the parties); and in human rights cases, a declaration of incompatibility under s.4 of the Human Rights Act 1998 (a declaration that an Act of Parliament is incompatible with a Convention right — the strongest statement the court can make, but it does not strike down the Act). JR is a remedy of last resort — if an adequate alternative remedy exists (such as an appeal to a tribunal), the court will usually refuse permission and require you to use that route first. See the habeas corpus entry for JR in detention cases and the statutory instrument entry for how secondary legislation can also be challenged by JR.