Mr Kennedy said that a Royal Commission should be created to look at the decriminalisation of cannabis and other soft drugs. The 39-year-old MP, who says he has never experimented with cannabis, is the first leader of a mainstream political party to urge such a major re-think of drugs policy.
He said the issue of drugs, the effect on crime rates and use for medicinal purposes should be subject to a thorough review by Parliament. Although proposals for a Royal Commission have been official Liberal Democrat policy for more than four years, the former leader, Paddy Ashdown, avoided the issue in the belief that it could damage the party's election chances.
Mr Kennedy made clear yesterday he was "under no illusions" that his critics would use his comments against him, but refused to accept that decriminalisation was a political minefield. "I don't know a household in the country that's not worried, extremely anxious about the whole issue of drugs," he told BBC Radio 4's The World This Weekend.
"It's what people are talking about out there. The fact that journalists and politicians in and around Whitehall and Westminster are not addressing these day-to-day concerns in a mature, considered and adult fashion is wrong."
As a "responsible politician", it was only right to ask why there were differing sentences handed out by the courts, and why senior police officers wanted change, he said. "I think we owe it to this country to have a better, more informed discussion and I think the best way is through a Royal Commission."
Downing Street insisted last night there was no need for an inquiry. "Tony Blair is against decriminalisation of cannabis and sees no value in a Royal Commission," a spokesman said. Ann Widdecombe, the Shadow Home Secretary, said that Mr Kennedy's remarks were "entirely the wrong signal" to send out to young people. "Charles Kennedy clearly has yet to learn how a responsible party leader should behave," she said. "This is an unbelievable first commitment which will alienate many of the people who put a cross by his name in the recent leadership election and who voted Liberal Democrat two years ago."
But support for Mr Kennedy came from an unexpected quarter when the Bishop of Edinburgh admitted he had tried cannabis and called for legalisation to be discussed. The Most Rev Richard Holloway, 65, said he had tried the drug and found it "disappointing", but believed cigarettes and alcohol were far more harmful.
Mike Goodman, director of the drugs charity Release, also welcomed Mr Kennedy's comments. "For a leader of one of the three main political parties to be making this statement now represents the drug debate coming of age," he said.
"Now is the time to talk, and consider not only the case to reform the drug laws, but also how a reformed system could be put into practice."
Review, page 3