Alice Cooper has offered Justin Bieber some sick advice - never turn your back on fans to vomit.

The old rocker, who incorporates theatre and gore in his live shows, insists Bieber has a lot to learn about showmanship and longevity if he is to become a seasoned pop star, and he was disappointed to hear the singer had thrown up onstage during a recent concert in Cooper's adopted Phoenix, Arizona.

Cooper tells, "He came into Phoenix, comes up on stage, turns his back to the audience and throws up. I said, in the press, 'Justin, just as a note of professional rock & roll, never turn your back when you throw up. Let the audience see you throw up... because that's a moment they're gonna remember. Make sure the lights are on you when you throw up.'"

But the shock rocker is a big fan of Bieber, and can only hope he survives all the excess and the pop star life.

Cooper adds, "If he rides this thing out and still makes records, he's gonna be a seasoned artist in about 10 years, 'cause he makes good records now, but he's got to survive the next 10 years. The excess is gonna come at him so quick."

Bieber suffered one of his worst weeks in London, where he arrived late for one show and struggled through illness to perform. He is currently on tour on mainland Europe.