Justin Bieber might be a troubled youth, but that does not give him the licence to brawl with the paparazzi or with his neighbours, feels Peter Mensch, manager of stage bands Metallica and Red Hot Chilli Peppers.

So what's the best way to ensure that Bieber behaves? Spanking.

"I'd take Bieber to the woodshed and spank him," said the 60-year-old, who believes that Bieber's career is over in three years. "His manager Scooter Braun is scared s***less. I don't know what Bieber's problem is. His career is over in three years anyway."

Mensch might prove himself correct if Bieber does not get his act together. Since the start of the year the 19-year-old pop star has been in the news for all the wrong reasons. After breaking up with his girlfriend Selena Gomez, the Canadian pop star was pictured smoking what looked like pot, which displeased a majority of his fans.

Over the years, Bieber has also become unprofessional, proof of it was the concert at London's O2 Arena last month. Bieber turned up two hours late for the performance and showed no remorse for keeping his young fans waiting.

Interestingly, Mensch is not the first person to voice out doubts about Bieber's career. Last year Sharon Osbourne told National Radio conference in Sydney that Bieber's fame is not long lasting.

"For me, Justin is.. I've met him, I've worked with him, I did a TV commercial with him. He's a really great little guy. But that's his problem. He's a little guy. His fans are growing up, they're eighteen, nineteen year olds now. And that means the little girls of titties and lips (sic), you know they're young women. And he still looks like that little boy.

"He needs some hair, or something. I just don't think, from my gut, maybe my guts wrong 'cos it's not a hundred per cent, but I don't think he's going to stand the test of time. But you know what, I don't feel sorry for him, because he's made oodles and he's a fabulously nice person and he'll go on to do something else."