A public authority is an authority that performs public functions; they are creatures of
Statute and derive its authority from statute. The source of its power being that of statute distinguishes public from private. Judicial Review is the jurisdiction of the superior courts to review laws, decisions, acts and omissions of public authorities in order to ensure that they act within their given powers. The judges exercise a supervisory power within the four corners of the Statute. NOTE: Public authorities exercise discretionary powers as a process of reasonableness and this discretion must be within the power given to them by the prescribed statute. If a public authority acts outside of the statute it is deemed Ultra Vires or unconstitutional.
However, the definition has been extended by case law to include some bodies which derive their authority from a source other than Parliament. This is due to a shift in the focus of the courts from looking at the source of power to the nature of the power. In
GCHQ case, we see the boundaries of Judicial Review of public bodies pushed. Here the body under review derived its authority not from statute but from prerogative power.
Lord Denning said that such a body should not be reviewed by the courts. However,
Lord Diplock held that there was a public element in the bodies function and there is no reason why the body should not be reviewable by the court.
NOTE: Lord Diplock set out three criteria s for a public body to qualify for judicial review. Illegality in the performance of its functions; Irrationality in the reasoning behind its decision; and Procedural impropriety
Exparte Datafin case went the furthest on the issue of a body subject to Judicial
Review. The case involved a private company run by private agencies