David Davis has made a vow of silence on drugs

The shadow home secretary said he did not want the issue to dominate the six-week contest.

He was speaking after his rival for the Tory crown David Cameron said he had never snorted cocaine as an MP.

Mr Cameron has previously dodged drugs questions, saying he had a right to a private life "before politics".

Dominated

The first test of Mr Davis's vow of silence came just six hours later when he was asked on Warwick University's student radio station if he took drugs in his youth.

Mr Davis replied: 'No I didn't take drugs. That's an old story. It goes back to 2001. And, if you'll forgive me, no more questions about drugs. I just won't answer them."

For the next six weeks I am not going to answer any questions on drugs, policy or otherwise David Davis 'Bad boy' Cameron keeps it real

Mr Davis earlier told BBC Radio 4's Today programme: "I have been asked questions about drugs policy which have invariably then been written up, rather mischievously I may say, as an attack on David and an attempt to put pressure on David.

"So I'm going to say this right now. For the next six weeks I am not going to answer any questions on drugs, policy or otherwise because I am simply not going to have this debate dominated by this issue."

Mr Davis is sensitive to claims he is trying to increase the pressure on Mr Cameron over the issue or even mount a smear campaign.

Final choice

The latest twist in the simmering Tory drugs debate came after Mr Cameron topped the final poll of MPs, beating Mr Davis by 33 votes.

With rival Liam Fox eliminated, Mr Cameron and Mr Davis face a six-week battle for the votes of the 300,000 Tory members who will make the final choice of leader.

Mr Davis says his visit to Warwick University, which is in Coventry, is symbolic of his desire to revive the Conservatives in the Midlands and north of England.

Asked what the difference was between himself and Mr Cameron, Mr Davis said: "David Cameron gives a lot more emphasis to the reform of the party. I give a lot more emphasis to the reform of the country."

'Compassionate Conservatism'

Mr Cameron began his campaigning with a visit to a community-run radio station in Brent South, north-west London, where he urged listeners to "keep it real".

Later, he met party workers in his Oxfordshire constituency of Witney and conducted an internet webcast.

Asked if now was the time to get into policy details, he said: "We cannot write the 2009 manifesto today."

But he vowed not to "lurch to the right" if elected leader.

"Cut me down the middle and I a modern compassionate Conservative," he told the webcast audience.

He said by the end of the campaign he hoped establish his own identity and shake off the label of the Tory's Tony Blair.

Mr Cameron said climate change was the most neglected area of government policy and he urged a cross-party consensus on the environment to take the issue out of party politics.