Mr Miliband insisted that "everybody" was entitled to a youthful past before they entered public life, adding that 33-year-old Mr Umunna is doing a "good job".

"I think everybody is entitled to a past, and a youthful past if you like, before they go into public life," Mr Miliband said.

"I think Chuka was asked a question and I think people are fed up with politicians not providing straight answers and he answered the question straight. I think that is fair enough.

"He is not taking drugs now, he is doing his job and he is doing a good job."

Mr Miliband's remarks come after Mr Umunna, a rising star in the Labour Party, admitted he had smoked marijuana when he was a teenager hoping to become a DJ. He said he briefly ran a club night in Brixton, south London.

"I've smoked soft drugs. But it's not something I'm proud of and I don't think it's news any more, to be honest," he said.

Asked what he had smoked, he said: "Certainly nothing beyond marijuana. That industry is rife with it."