The Government's chief drugs adviser forced to resign by Home Secretary Alan Johnson has admitted that his children have taken illegal substances.
Professor David Nutt said more than one of his four adult children had confessed to taking drugs.
But the scientist told the Mail on Sunday that he believed alcohol posed a greater risk to young people and that was where the "big effort" should be concentrated.
Prof Nutt stepped down as chairman of the Advisory Council on the Misuse of Drugs on Friday after Mr Johnson said he had "lost confidence" in his ability to give impartial advice.
There has been speculation that more advisers will resign after scientists criticised Mr Johnson's stance, saying the Government should listen to its experts.
Prof Nutt said he was more concerned about the risk of alcohol to young people than drugs, adding: "I'm sure my children have tried drugs. In fact, some have told me they have. But I'm not as concerned about this as I am about alcohol."
Prof Nutt, who has four children aged 18 to 26, said alcohol was a greater risk to young people because it was "cheap, readily available and accepted". He said it could lead to "risky behaviour" and killed several children a night.
"That's what we should be telling our kids and that's where our big effort should be," he said.
He criticised Gordon Brown for saying cannabis was a lethal drug when clearly it was not, and said young people would ignore the Government if it did not tell the truth.
The row which forced Prof Nutt's resignation was due to comments he made that ecstasy and LSD were less harmful than alcohol and cigarettes. He also criticised the decision to upgrade cannabis to class B.
