Tory leadership hopeful Michael Gove said he was lucky to have avoided jail for cocaine use - but denied allegations of hypocrisy.
The Environment Secretary said "drugs wreck lives" and his cocaine use was a "mistake which I profoundly regret".
The Cabinet minister has admitted taking the drug on several occasions around 20 years ago when he was a journalist.
Read more: Tory leadership contender Michael Gove 'deeply regrets' taking cocaine
Asked if he should have gone to prison, Mr Gove said: "I was fortunate in that I didn't, but I do think it was a profound mistake and I have seen the damage drugs do."
The former justice secretary said: "I have seen it close up and I have also seen it in the work that I have done as a politician.
"That is why I deeply regret the mistake that I made."
Metropolitan Police chief Cressida Dick has told middle-class drug users they have "blood on their hands" for financing a trade that results in gangland violence and the deaths of youngsters on the streets.
Mr Gove told BBC One's Andrew Marr Show: "I hugely respect Cressida Dick. One of the things that I would absolutely say is it is a mistake which I profoundly regret. Absolutely.
"One of the things that I also completely agree with is that the drugs trade is wrong, that drugs wreck lives and that's one of the reasons why I have sought, in office, to try to help people to move away from that."
Read more: Euan McColm: Tory contenders admit drug taking but can’t face Brexit reality
Mr Gove faced claims of hypocrisy over a column he wrote for The Times hitting out at "London's liberal consensus" around decriminalisation of drugs.
According to the Mail on Sunday, Mr Gove hosted a party the night before the column was published in which the Class A drug was allegedly taken by guests.
Asked by Marr whether he was a hypocrite, Mr Gove said: "No. I think anyone can read the article and make their own minds up. The point that I made in the article is that if any of us lapse sometimes from standards that we uphold, that is human.
"The thing to do is not necessarily then to say that the standards should be lowered. It should be to reflect on the lapse and to seek to do better in the future."
The Environment Secretary insisted that his cocaine confession would not bar him from entry to the United States if he became prime minister and it was "foolish to suggest otherwise".
He said "no-one asked" about it when he became a government minister.
He said "I don't believe that I have ever on any occasion failed to tell the truth about this when asked directly".
Home Secretary Sajid Javid, a leadership rival to Mr Gove, told Sky News "It's not for me to pass judgment on fellow candidates" but added: "People do need to know - it doesn't matter if you are middle class or not - anyone who takes class A drugs, they need to think about that supply chain that comes from Colombia, let's say, to Chelsea and the number of lives that are destroyed along the way."