Mark Wahlberg has warned Justin Bieber not to ''be so naughty.''

The singer turned actor - who was jailed for assault as a teenager - warned the 'Beauty and a Beat' hitmaker to stop smoking cannabis and focus on his career.

During a webchat with The Sun newspaper, he joked: ''Justin are you listening? Don't be so naughty, yeah?

''Be a nice boy, pull your trousers up, make your mum proud, and stop smoking weed, you little b***h.''

On a more serious note, Mark, 45, added: ''He's a teenager living in a different day and age. I was in prison before I got a record out and I don't think he's been to prison.

''He's a nice enough kid and you're going to be a teenager. But if you're being a teen in the spotlight you're going to be criticised for it.

''This career can be short lived - you might as well be the best you can while you're doing it.''

Mark - who rose to fame as the leader of pop group Marky Mark and the Funky Bunch - is also planning to work with the 19-year-old heartthrob on a film and may even get behind the mic again for the soundtrack.

He said: ''Justin and I were talking about doing a movie, which could still happen.

''We have a great script which could be a vehicle for him to make his debut in movies, then maybe we could do something for the soundtrack.''