Billie Joe Armstrong's bandmate wasn't surprised by his public meltdown last year that led to him going to rehab for 30 days.

Green Day bassist Mike Dirnt has revealed the group ignored warning signs that the 41-year-old 'Basket Case' singer was struggling to cope with his addictions to alcohol and drugs because they were too busy.

He told Rolling Stone magazine: ''We all turned a blind eye to it - 'Everyone, deal with your own s**t.' Because we were working so hard.''

Mike, 40, said the turning point was when the group's front man had a breakdown on stage in Las Vegas last September, when the group was performing at the star-studded 'iHeartRadio Music Festival', during which he screamed profanities and slammed Justin Bieber before violently smashing his guitar on-stage, complaining their performance had been cut short.

He said: ''Truth be told, I agreed with what he said, outside of mentioning anybody else. I know that's not Billie. But the bigger side of it - I actually agreed with the rant. But I was watching my friend and going, 'You're out of your f**king mind.' And we were dealing with a s**tshow.''

The rockers have now made some changes to try to help Billie stay sober while on tour.

Mike said: ''The backstage doesn't need to be a bar. And that's OK with me. That's just time-killing, coping mechanisms. Also, we don't have to say yes to every opportunity in front of us. We did something like 228 shows for 'American Idiot' and 190 for 21st Century Breakdown. And that doesn't include band practice five days a week in between.

''My thing is, good, bad or ugly, I gotta support my boy. I'm gonna back him up, and then I'm going to take it the next step further with him. And we're gonna do it offstage, too.''

Billie recently revealed he is committed to staying sober after battling addictions for almost 20 years with the help of ''meditation through prayer''.