Q: Mr Howard, have you ever smoked dope? A: No comment

It is the question that most politicians dread: "Have you ever smoked cannabis?" David Blunkett tried to turn the tables on Michael Howard yesterday by challenging him to say whether he had ever used the drug after the Tory leader pledged to reverse the Government's decision to downgrade cannabis.

The Home Secretary unwittingly provoked a fresh controversy about whether politicians should be required to disclose their own experiences with drugs in their younger days. Mr Howard, in an interview in The Independent yesterday, accused the Government of creating a "muddle" by deciding to reclassify cannabis as a Class C drug, but refused to disclose whether he had ever used it himself.

Mr Blunkett told BBC Radio 4: "Let's ask him [Mr Howard] 'Did you ever smoke it?'" Asked what his response would be if Mr Howard were to admit he had smoked cannabis, Mr Blunkett said: "I would say fine, thanks for being honest, now what would you have done to you? What would your parents have said if we had picked you up for smoking it, criminalised you and had you banged up in jail?"

The Home Secretary said he had never smoked cannabis. "But if I had, I would be quite transparent about it because 40-odd per cent of under 30-year-olds have," he said.

Inevitably, Mr Blunkett was asked if Tony Blair had ever taken the drug. He said: "Goodness me, he played the guitar very well, but it is not synonymous with having a puff."

Downing Street was less than amused that Mr Blunkett's remarks prompted questions about Mr Blair's personal history. The Prime Minister's official spokesman tried to play down the remarks as "political knockabout" and declined to say whether Mr Blair had ever smoked cannabis.

Outlining the Tories' strategy during a visit to Hertfordshire yesterday, Mr Howard again refused to discuss his personal drugs policy in the 1960s.

He said: "No, that's not a question I am going to answer. When the Government was asked in October 2000, all the ministers said we are not going to answer that question, and I don't think it would be sensible - I don't want you to go round all the Shadow Cabinet asking the question."

In October 2000 there was a fiasco over the "zero tolerance" drugs policy announced by Ann Widdecombe, then shadow Home Secretary, at the Tories' annual conference. She proposed £100 in fixed-penalty fines for people caught even with small amounts of cannabis. But her policy went up in smoke after seven senior Tories admitted that they had smoked cannabis in their youth: Oliver Letwin, who said his pipe had been "spiked" with the drug; David Willetts; Francis Maude; Peter Ainsworth; Archie Norman; Bernard Jenkin and Lord Strathclyde. "The magnificent seven," as Tory aides described them, became eight when Tim Yeo admitted that he also had experimented with cannabis as a student.

Such recreational pursuits were not, of course, confined to Tories. Some Labour ministers have also admitted smoking cannabis in the past - including Caroline Flint, the Home Office minister who yesterday launched a £1m advertising campaign to explain the reclassification of cannabis.

Yvette Cooper, a minister in John Prescott's Office of the Deputy Prime Minister, gave an unusually straight answer to the question most politicians dread when she appeared on BBC Radio 4's Any Questions the week after the Tory policy collapsed. She said: "I did try cannabis while at university, like a lot of students at that time, and it is something that I have left, you know, behind, and it was several years ago."

Most of the other Labour ministers were less forthcoming. They were advised by Downing Street to tell prying journalists: "We don't take part in surveys."

Mo Mowlam, the former Secretary of State for Northern Ireland, was one of the few prepared to speak her mind and admit that she had smoked cannabis. As a Cabinet Office minister, she was responsible for the Government's drugs policy but failed to wean her cabinet colleagues off the hardline approach adopted by Mr Blair, who once carpeted Clare Short for suggesting that cannabis should be legalised.

Since leaving Parliament, Ms Mowlam has called for the legalisation of all drugs, including heroin and cocaine. She said in 2002 that the money raised from taxing drugs could be used to treat addicts. She said: "If the kids get hold of it because it's a high, they will get hold of it. Why not regulate it, take the tax from it and deal with addiction?"

Ms Mowlam also admitted that she had inhaled, unlike Bill Clinton, who fittingly adopted the "third way" policy of saying that he had tried cannabis but did not inhale it - rather similar to his reply to the Monica Lewinsky question.

'Did you ever smoke it?'

Tony Blair: "The one thing my father really drummed into me was never to take drugs."

David Blunkett: "I never felt the need to try drugs. Life was challenging enough without getting stoned."

Mo Mowlam: "I did inhale" [unlike former US president Bill Clinton]

Archie Norman: "I don't regret having done it. You expect people to experiment. If you don't you haven't been young."