Virgin tycoon Sir Richard Branson has revealed how he enjoyed the high life, by taking drugs with his son and having sex on a plane when he was a teenager.

The extrovert billionaire told how he smoked cannabis with model son Sam, now 21, during a surfing holiday in Australia.

Sir Richard, 57, of Mill End, Kidlington, said: "I went with my son on his gap year. We had some nights where we laughed our heads off for eight hours."

He added: "I don't think smoking the occasional spliff is all that wrong. I'd rather my son did it in front of me than behind closed doors."

In an interview with GQ magazine, the entrepreneur also admitted trying cocaine and ecstasy.

He said: "I took ecstasy once. But it didn't have a massive effect on me".

Of cocaine, he said: "I suspect I've tried it, yes."

The businessman, reportedly worth £5bn, claims Rolling Stone Keith Richards was the "first person to teach me to roll a joint".

He said he had not tried super-strong "skunk" cannabis and added: "I think that skunk is far too strong and dangerous and it should be banned."

Anti-drug campaigners condemned Sir Richard's drug-taking.

Peter Stoker, director of the National Drug Prevention Alliance, said: "Richard Branson as a parent should know better than to take health-endangering drugs with his child. It was irresponsible and sets a bad example.

"From what I can gather this took place three years ago, but it would be even more irresponsible now because a lot more has been learned about the harmful effects of cannabis, both mental and physical.

"Young people might look upon Sir Richard as a role model but it would be false to link his financial success with smoking cannabis with his son."

In the interview, Sir Richard also described how he became a member of the "mile-high" club with a married woman.

He said: "I was sitting in economy on a Freddie Laker flight, next to this very attractive lady, as we headed to LA.

"We got chatting and it went a bit further. And it was every man's dream, to be honest. I was about 19, I think."

Sir Richard, who owns more than 350 companies, also recalled how he took the sex pill Viagra.

Sir Richard's daughter Holly, 26, has been linked to Prince William, but the billionaire said the pair were "just good friends".