Mr Cameron, 39, is widely thought to have allowed David Davis back into the Tory leadership contest after his rival won a points victory in their head-to-head debate on the programme on Thursday night.
He sounded rattled yesterday when he claimed he did not care "what other people think'' after the Home Office dismissed as "irresponsible" his remarks on the programme in support of ecstasy being downgraded from its current status as a class A drug.
It is the second time Mr Cameron has become embroiled in a row over drugs having earlier refused to say whether he tried drugs as a student and the issue threatened to engulf his campaign. Last night his supporters were calculating what, if any, damage the re-emergence of the issue would have as more than 250,000 ballot forms were sent out to Tory members for the leadership election.
Mr Cameron said he was standing by remarks about downgrading ecstasy during his head-to-head clash with Mr Davis, 57. "What people want is a realistic and sensible policy that gets to the bottom of the drugs' problem," he said yesterday while seeking votes from Conservative Party members in Winchester.
He added he wanted to see ex-drug addicts going into schools to talk about the dangers of drugs and also to tell pupils the difference between substances such as heroin and ecstasy.
Mr Cameron said this was a "tough" drugs policy. He added: "Frankly I do not care what other people think about it."
Earlier there appeared to be an attempt by his aides to distance Mr Cameron from his comments on the programme which could do his leadership campaign harm among traditional Tory supporters, especially as they came on the tenth anniversary of the death of Leah Betts from ecstasy. His spokesman confirmed the issue would be examined if he became leader but added: "It would be a matter for the party to decide."
Charles Clarke, the Home Secretary, made it clear he had no intention of lowering the classification of ecstasy. He said: "Ecstasy can and does kill unpredictably and there is no such thing as a safe dose."
Mr Cameron's support for reclassifying the drug stemmed from a term on the cross-party Commons select committee on home affairs, which recommended that the Home Office should change the law on ecstasy and cannabis. Its recommendations were rejected by the Home Office and attacked by then Tory leader, Iain Duncan Smith.
Members of the Cameron team insisted his stance would not damage his prospects because he had been consistent. Ken Clarke, the former Chancellor, who still carries support in the country, said he was inclined to support Mr Cameron but he admitted in a GMTV interview to be screened tomorrow "he is a bit of an unknown quantity, even to me to a certain extent".
During Thursday night's programme, Mr Cameron said: "The most important thing we thought was to make sure that the drug classifications make sense to young people and were credible. And I had a concern that if you put ecstasy and heroin in the same classification, people just don't take it seriously."
Asked specifically about downgrading ecstasy, he said: "Yes. I think that is right, looking at the science."
Mr Davis, the shadow Home Secretary disagreed, saying: "Ecstasy has been responsible for deaths - Leah Betts most obviously, but others as well."