Judicial Review and Prerogative Powers


The issue in judicial review proceedings is not whether the decision was right or wrong, nor whether the court agrees with it, but whether it was a decision that the decision-maker was lawfully entitled to make.

Basic grounds of challenge:


This arises iwhen the public body:

  • misdirects itself in law, such as by 'getting the law wrong' or asking itself the wrong legal question
  • exercises a power wrongly, such as by purporting to act in pursuance of one statutory objective but applying the wrong legal test under that objective
  • purports to exercise a power that it does not have. Using this ground, it would be possible to challenge a decision of a public body that is inconsistent with an Act of Parliament or delegated legislation; or
  • exercises its power for an improper purpose that is not the purpose for which the particular power was granted

Irrationality / Unreasonableness

 A decision can be challenged as irrational or unreasonable in limited circumstances, namely if:

  • it  “is so unreasonable that no reasonable authority could ever have come to it.." (Wednesbury unreasonableness); or
  • the public body, in reaching its decision, took into account irrelevant matters and/or failed to consider relevant matters

Despite attempts to broaden the scope of judicial review, the courts are very reluctant to challenge decisions as unreasonable. This grounds of appeal implies that the merits of the decision (that is, whether the public body made the right decision) is not within the scope of review.

It may be easier to establish a claim based on a failure to take proper account of appropriate considerations than pure unreasonableness. It is clear that the error must be material to the decision to establish illegality. The test has been described as being: "whether a consideration had been omitted which, had account been taken of it, might have caused the decision-maker to reach a different conclusion" (R v Parliamentary Commissioner for Administration, ex parte Balchin [1998] 1 PLR 1).

 Procedural Impropriety

The ground of procedural unfairness arises if:

  • the public body has not properly observed relevant procedures such as a requirement to consult on the proposed measures; or
  • the public body has failed to observe the principles of natural justice, such as by showing (apparent or actual) bias

Legitimate Expectations

A potential challenge may be founded on the basis of breach of a legitimate expectation in that the public body may, by its own statements and/or conduct, be required to act in a certain way, where the affected party has an expectation as to the way in which the public body will act. A successful judicial review founded on breach of a legitimate expectation will arise only in a limited number of cases.

A legitimate expectation may:

  • have both substantive and procedural dimensions, and therefore overlaps with irrationality and procedural impropriety
  • be substantive where the appellant has an interest in some benefit that it hopes to obtain, and fairness may require that expectation to be upheld if it is shown that the appellant relied on the expectation to his detriment. The court is generally slow to find a substantive legitimate expectation
  • arise where the public body has made a clear representation that it will adopt a particular procedure and then the public body departs from that purported procedure

Regulation of Prerogative Powers

Traditionally, the courts do not have power to regulate the way in which prerogative powers are exercised, even though the existence and the extent of the prerogative power may be reviewed by the courts.

However, there has been a gradual recognition by the courts that they can review the exercise of prerogative powers.

In CCSU v Minister for Civil Service ([1983] UKHL6), it was held that the exercise of prerogative powers was not automatically outside the scope of judicial review. The only exception was if the power being exercised was not justiciable (that is, not an appropriate area for the courts to be involved in).

These are essentially areas of high politics. It is the nature of the power rather than its source that determines justiciability.