David Cameron receives a public warning today that he will face political trouble if evidence emerges that he experimented with more serious drugs than cannabis or tried drugs after leaving university.

A new Populus poll for The Times shows that there is strong public support for the Conservative leader and his refusal to discuss whether he smoked cannabis when he was at Eton 25 years ago.

The poll was undertaken on Tuesday after the appearance of allegations in the Sunday papers that, when aged 15, Mr Cameron was punished after admitting that he had smoked cannabis.

More than four fifths of the public (81 per cent) believes that it does not matter if Mr Cameron smoked cannabis when he was at school or university. Eighty-five per cent believe that he should not be expected “to answer detailed questions about whether he tried drugs in his youth because all politicians are entitled to have made mistakes when they were growing up”.

This tolerant attitude is not open-ended. Nearly two thirds (64 per cent) say that “it would matter if he had experimented with more serious drugs” at school or university.

Nearly three quarters of those questioned (71 per cent) say that, although it does not matter if Mr Cameron tried drugs when he was at school or university, “it would matter if it turned out that he had done so as an adult, after he started work”.

During the Conservative leadership campaign in autumn 2005, Mr Cameron refused to reveal whether he had taken drugs either at school and university or, later, before he became an MP in 2001.

On Sunday, after the charges emerged about his use of cannabis at Eton, he said: “Like many people, I did things when I was young that I should not have done, and that I regret. But I do believe that politicians are entitled to a past that is private, and that remains private.”

That line is not only backed by a large majority of the public but is the view of most Conservative MPs. The other main parties have remained generally silent about the charges, which will be made in a new biography, Cameron, The Rise of the New Conservative, by James Hanning and Francis Elliott, which is due to be published in early April.

Women are less relaxed on the question of the use of more serious drugs: 69 per cent say that it would matter, against 59 per cent for men.

There are marked age differences. Younger people are much more supportive of Mr Cameron than older ones: 90 per cent of 18 to 34-year-olds say that it does not matter if he smoked cannabis at school or university, against 71 per cent among those aged over 55.

Just 53 per cent of those aged 18 to 34, but 71 per cent of over55s, say that it would matter if had experimented with more serious drugs.

While two thirds (66 per cent) of 18 to 34-year-olds think that it would matter if Mr Cameron had tried drugs as an adult after he started work, this rises to three quarters (75 per cent) among over55s.

Populus interviewed a random sample of 522 adults aged over 18 by telephone on February 13. Interviews were conducted across the country and the results have been weighted to be representative of all adults. Populus is a member of the British Polling Council and abides by its rules. For more details go to www.populuslimited.com .

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