|Justin Bieber and Mark Wahlberg|
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."