JUDICIAL review (JR) is often talked about – and feared – but rarely understood. Put simply, it is a mechanism by which decision making by public authorities can be challenged in the High Court.

The power to apply for a JR remedy is a prerogative, which means that, in legal theory at least, it is exercised by the Crown on behalf of the applicant.

A review is fundamentally different from an appeal because it concentrates on the legality of the decision in question. In other words, it looks for a legal error in the way in which the decision has been taken, rather than carrying out an assessment of the merits of that decision.

If there is no legal error, a JR challenge will not be successful. Equally, the judge does not make a new decision to substitute that of the original decision taker.

The object of the review is either to quash the decision (and remit it back to the decision taker for a new decision to be made) or to order the decision taker to do, or refrain, from doing something.

Typical grounds of review are where a public authority has stepped outside permitted procedure, has failed to have regard to a relevant issue, has had regard to an irrelevant issue or has acted irrationally.

Local authorities, for example, must operate within their statutory powers and, in many cases, are given discretion as to how or whether they exercise a statutory power. That discretion must be exercised reasonably. If not, it is potentially open to challenge by JR.

However, JR is not appropriate in all cases where public authority decision taking has fallen into legal error. If there is a right of appeal against the decision, then the courts have consistently required the appeal route to be taken instead, for example in the planning system.

JR can be a very expensive means of redress because it must begin in the High Court, and often necessitates specialist legal advice and drafting. Until earlier this year, the High Court in London was the only venue. but this has now been opened up to Leeds and Manchester.

The first step in the process is to make an application for permission to apply for JR, usually decided upon the case papers without the need for a hearing. Only in the event that permission is granted will the application proceed to a full hearing in court.

JR proceedings must be commenced promptly and in any event not more than three months from the date of the decision to be challenged.

Potential applicants must move quickly to instruct specialist lawyers at the earliest possible stage.

In some cases, most notably in the planning system, a quasi judicial review mechanism exists which requires challenges to Planning Inspectorate/Secretary of State decisions to be brought within six weeks of the relevant decision.

■ Neil Carter is a solicitor at BHP Develop specialising in planning and local government law and can be contacted on 01642- 672770.