David Cameron smoked cannabis while at secondary school, a new biography has claimed.
Today's allegations about the Conservative leader's alleged misbehaviour as a teen come in a biography by journalists Francis Elliott and James Hanning published in the Independent on Sunday newspaper.
The book cites contemporaries of Mr Cameron claiming that the 15-year-old Conservative leader-to-be was disciplined for smoking cannabis after confessing his misdeed to teachers.
Conservative party officials shrugged off the allegations, pointing out "this happened almost 25 years ago".
Making a brief statement outside his family home, Mr Cameron said: "Like many people I did things when I was young that I shouldn't have done and that I regret. But I do believe that politicians are entitled to a past that is private and that remains private and so I won't be making any commentary on what's in the newspapers today.
"That's really all I have to say on what for me is an important family day," he added.
Political analysts have said traditionalists within the Conservative party, already uneasy with their new leader's liberal-leaning agenda, disapprove of this incident.
Party grandee Lord Tebbit told BBC News yesterday that although disapproval was to be expected, he believed transgressions made while still a teenager should not prevent politicians from achieving high office.
"I think we have to take a reasoned view about these things, and the question now is whether or not he understands it is a highly dangerous drug and should be treated as such," Lord Tebbit said.
Current politicians took a more liberal attitude.
Shadow foreign secretary William Hague commented: "This makes no difference to my view of him or, I think, the view of most people in the country.
"He has always been very clear that your life before you went into politics is a private life and it should be possible to have that as a private life, and he has always been absolutely consistent about that."
And home secretary John Reid agreed.
"I think this is one of those 'so-what' moments," Mr Reid told the BBC One's Politics Show.
"Do we want to get to the level of ensuring that every politician... is a sort of plastic politician produced off some colourless and characterless conveyor belt?"