One of England's oldest and most distinguished Catholic state-funded boys' schools has won a High Court action over a finding that its admissions criteria was socially selective, discriminatory and unfairly disadvantaged children from less well-off families.

A judge in London said that this conclusion by an education watchdog relating to The London Oratory School - whose pupils have included the sons of former prime minister Tony Blair, Liberal Democrat leader Nick Clegg and deputy Labour leader Harriet Harman - was "flawed" and must be quashed.

Mr Justice Cobb said that a school adjudicator's decision on that issue was "reached by a process which was procedurally unfair to the school".

An Office of the Schools Adjudicator (OSA) investigation was triggered by a complaint from the British Humanist Association about the faith-based criteria used to select pupils for places at the heavily oversubscribed Catholic academy, founded in 1863.

The school went to the High Court to challenge a number of OSA findings that many aspects of its arrangements for 2014 and 2015 breached the schools admissions code.

Following a hearing last month, Mr Justice Cobb today announced his decision in the case. He quashed some of the adjudicator's findings, but upheld others.

The judge said: "It is highly regrettable that the two investigations undertaken in relation to this school since May 2013 have now been shown in material respects to be flawed.

"While I believe that the adjudicator has, in the main, endeavoured to fulfil his responsibilities conscientiously for the long-term benefit of the school, the candidates and their parents, his approach to his task in the specific respects set out (in his ruling) have in my judgment been shown to be unlawful and/or unreasonable and cannot stand.

"This will be of little comfort to the school which has, I am sure, found this process extremely challenging."

"The allegation, which made headline news, that the school was socially selective and discriminating against less well-off families has been hurtful to staff, pupils and parents. This damaging allegation has been found by the judge to be wrong and unfair, and the finding vindicates the robust approach the school has had to take against the Office of the Schools Adjudicator."

Ane Vernon, school solicitor

"The judge's decision supports us in continuing to preserve the school's ethos and serving Catholic families throughout the whole of London."

David McFadden, Headmaster