Green Day can still call themselves punks, despite becoming a commercial success, according to frontman Billy Joe Armstrong.

The band have been criticised for abandoning the true meaning of punk and selling out.

But Armstrong insists they've never lost their punk roots.

He says, "Sometimes I think we've become totally redundant because we're this big band now, we've made a lot money - we're not punk rock any more. But then I think about it and just say, 'You can take us out of out a punk rock environment, but you can't take the punk rock out of us.'

"When we started it was a proven fact that punk could not get popular. So we never played punk rock to get famous."