The right of the schools admissions watchdog to cut selection in schools has been rejected in a High Court ruling.

The ruling backs a challenge from the London Borough of Wandsworth against the admissions adjudicator's decision to reduce selection in the borough.

But changes in legislation introduced last autumn make it unlikely that this will affect future decisions over admissions and levels of selection.

A spokesman for the Education Department said: "This is the first and last time there can be an appeal like this."

The number of school admissions disputes has risen in recent years

The High Court ruling on Friday says that the Office of the Schools Adjudicator was acting unlawfully when it sought to impose a reduction in selection by ability in three secondary schools.

The Wandsworth schools had been required by the adjudicator to reduce substantially the number of selected pupils - a decision which the authority claimed was an unfair and unlawful restriction.

The adjudicator had intervened after complaints from governors of primary schools and local parents about Wandsworth's partially-selective secondary schools.

There had been concerns that many local children living close to the schools were unable to gain places there.

Two of the schools, Ernest Bevin College and Graveney, select 50% of their pupils by academic tests, which the adjudicator wanted to reduce to 25%.

The third school, Burntwood, selects 30% of its pupil on ability and had been instructed to lower this to 25%.

The local authority, in its appeal against the reduction in selection, said that such a change in policy would represent a substantial change in the whole character of the schools - a shift that the admissions adjudicator had no right to impose.

Selection can be based on the results of written tests

Parents who had called for less selection say that they will apply again next year for a change in admissions, under the revised regulations.

"Wandsworth have found a legal nicety on which to rely in order that they can continue this appalling policy, which means children living next to these schools can't go to them," said John Valentine of the Campaign for Local Education.

"Children are coming from all over the home counties to take places in these schools that should be going to local children."

But the Shadow Education Secretary, Theresa May, said the case had really been about "Labour's plan to end selection by stealth. We oppose the appointment of unelected adjudicators, who make decisions that fly in the face of local people".

The Office of the Schools Adjudicator was set up by the government last year to rule over the growing number of disputes about admissions to schools, and to enforce the official code of practice for the allocation of places.

Among the other local authorities in which admissions rulings on schools have been or are to be made are Barnet, Bexley, Bromley, Croydon, Hertfordshire, Northamptonshire, and Surrey.

Among the earlier judgements was a cut in selection from 45% to 10% at the Mill Hill County High School in Barnet, north London.