Billie Joe Armstrong was a ''functioning alcoholic'' before he entered rehab.

The Green Day singer's drinking and reliance on prescription drugs had got out of hand before he was finally admitted to rehab last September and he admits to frequently being intoxicated on stage.

He told Rolling Stone magazine: ''I played onstage loaded a lot. I'd have anywhere from two to six beers and a couple of shots before I went onstage, then go and play the gig and drink for the rest of the evening on the bus.

''Fall asleep, wake up the next day, feel like s**t, do soundcheck. It was over and over again. In that way, I was a functioning alcoholic.

''I've been trying to get sober since 1997, right around 'Nimrod'. But I didn't want to be in any programmes.

''Sometimes, being a drunk, you think you can take on the whole world by yourself.''

He also talked about how he used to carry so many prescription drugs his ''backpack sounded like a giant baby rattle.''

He added: ''I started combining them to a point where I didn't know what I was taking during the day and what I was taking at night. It was just this routine.''

Things came to a head at the iHeartRadio festival in Las Vegas last year where even Billie's bandmates Tre Cool and Mike Dirnt were stunned at his behaviour, after they were told by teleprompter the band's set was being cut short and they only had one minute left to play.

In response, Billie shouted: ''You're going to give me one minute? One f**king minute? I've been around since f**king 19 f**king 80 f**king eight, and you're going to give me one f**king minute? I'm not f***ing Justin Bieber, you motherf***ers.''

He then destroyed his guitar and left the stage. The band are now preparing to make their live comeback, which will take place this month.