The Prime Minister's 17-year-old son, Euan, has been made a deputy head boy of his school, the London Oratory, it has been revealed.

He has been appointed as one of four deputies at the school, which is in Fulham in west London.

According to the Times Educational Supplement, Euan's mother, Cherie Blair, was in the audience at the school prize-giving ceremony last week, when the appointment was announced.

He will take on his new role next term, for his final year.

"Drunk and incapable"

Last summer the 17-year-old was reprimanded by police after being found lying unconscious, "drunk and incapable" late at night in London's Leicester Square after celebrating the end of his GCSEs.

The head teacher of the London Oratory is John McIntosh, who belongs to the National Association of Head Teachers, which is meeting for its annual conference in Harrogate, North Yorkshire.

The general secretary of the union, David Hart said he backed Mr McIntosh's judgement.

"If John thinks Euan Blair is fit to be deputy head boy then all power to Euan," he said.

Mr Hart said he did not think that the fact that Euan had been found drunk under-age in the West End should have prevented him from being chosen.

He said: "If every head boy or head girl was to be disqualified because they had been found in an inebriated state at some stage in their school life then we would see a lot of head boys and girls disqualified from fulfilling that office.

"Boys will be boys and girls will be girls."

Downing Street refused to comment. A spokeswoman said: "We never discuss the children."