MALCOLM TURNBULL last night became the first Liberal leader to admit he had smoked marijuana.

On ABC1's Q&A program the host, Tony Jones, began asking: "Have you ever…" when Mr Turnbull headed off the question by saying: "smoked dope? Well, yes I have."

He said he had smoked marijuana in his much younger days and now thought it was a very bad idea because the drug could be damaging. "Many people have [smoked it]," he said, before adding it was a mistake to do so.