On the BBC One Question Time programme Mr Cameron was asked directly for the first time whether he had used hard drugs. He has been under increasing pressure to disclose any history of drug use since he was first asked at the Conservative Party conference in Blackpool last week.

He gave his most extensive — and most defiant — response on the issue to date. Mr Cameron, the 39-year-old Shadow Education Secretary, who has soared ahead in the leadership polls after a popular speech last week, hinted about “mistakes” that he had made in his youth. But at the same time he said that he would not give in to a “witch hunt” over whether he had used drugs, refusing to reveal more details because “that was all in the past”.

“I’m allowed to have had a private life before politics, in which we make mistakes and we do things that we should not — and we are all human and we err and stray,” Mr Cameron said on the programme.

“And I think if you want to have machines as politicians who have never done anything wrong, I think that is a very sad day and we should not be driven by the media on that.”

His response drew applause from the audience, but the MP for Witney now finds that his campaign is dominated by the drugs question before the first ballot of MPs in the Tory leadership race on Tuesday.

He was bullish about his decision to remain tight-lipped last night, despite criticism from fellow panellists such as Mark Oaten, the Liberal Democrat Home Affairs spokesman.

“I didn’t spend the early years of my life thinking ‘I better not do anything because one day I might be a politician’, because I didn't know I was going to be a politician,” Mr Cameron said. “And I haven’t answered the question about drugs because I think that’s all in the past and I don’t think you have to answer it.”

Mr Cameron made the distinction between a politician’s life before he held office and his current responsibilities. “I think you shouldn’t be a law-breaker and a law-maker,” he said.

He cited in his defence the debacle in 2000 when Ann Widdecombe, then Shadow Home Secretary, called for a tougher line on cannabis. After her comments, eight members of the Tory Shadow Cabinet admitted to having smoked the drug. Mr Cameron also pointed out that Tony Blair, the Prime Minister, has never categorically denied drug use in his youth, saying instead that the never “got into drugs”. “I have seen Conservative Shadow Cabinets pulled apart by this question with different people giving different answers,” said Mr Cameron.

“The Labour Cabinet have not answered this question. They have said it is not relevant now.”

However, Mr Cameron’s three main rivals, David Davis, Ken Clarke and Liam Fox, have each denied ever using any kind of illegal drug and there is a suspicion that politicians in opposing camps could exploit Mr Cameron’s coyness on the subject.

The question first arose when Mr Cameron was asked whether he had ever taken drugs, at a fringe meeting of the Conservative Party conference in Blackpool. He simply said that he had had a typical student experience, but when confronted by the issue again in a television interview on Sunday, he said: “I did lots of things before I come into politics which I shouldn’t have done. We all did.”

Mr Cameron has previously backed the relaxation of drug laws.

DRIFTING SMOKESCREEN

May 24
In a Commons speech David Cameron says that raising school standards would address problems that the nation faces over skills, crime and drugs

September 6
He says he believes that the UN should consider legalising drugs

October 5
Cameron is asked, in an interview at a fringe meeting at Blackpool, if he has ever taken drugs. He refuses to say whether he has

October 6
Pressure increases on Cameron, dubbed by some tabloid newspapers as “Cannabis Cameron”, as he continues to refuse to answer the question

October 9
All his rivals indicate that they have never taken illegal substances

October 11
Appears to accidentally admit to smoking cannabis but continues to duck challenges or deny smoking the drug as a younger man

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