Actor Mark Wahlberg has warned teen superstar Justin Bieber to clean up his act and behave more appropriately or risk ruining his career. The Baby singer has hit the headlines for all the wrong reasons in recent months for his increasingly bizarre behaviour, and Wahlberg is hoping the 19 year old will follow his example and turn his life around. The Fighter star served 45 days in prison after pleading guilty to an assault charge at the age of 16, and the actor swears the conviction was a turning point in his life. Speaking during a live web chat with Britain's The Sun, Wahlberg, who shot to fame as a member of pop group New Kids on the Block, implored Bieber to change his ways and abstain from drugs. He says, "Justin, are you listening? Don't be so naughty... Be a nice boy, pull your trousers up, make your mum proud and stop smoking weed you little b**tard. 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." Wahlberg was previously in talks to work with Bieber on an acting project, but the basketball-themed movie was put on hold following a raft of setbacks. Bieber's most recent troubles have included police finding marijuana on his tour bus, while a night out in New York on Saturday (03Aug13) prompted a police investigation over allegations members of his entourage were involved in a brawl.