Justin Bieber sorry for racist joke

Justin Bieber attending the Amber Fashion Show and Charity Auction at Le Meridien Beach Plaza Hotel in Monaco, on May 23, 2014. Credit: Press Association Images

Justin Bieber has apologised after a video was leaked online showing the popstar making a racist joke in 2011.

"I'm very sorry," Bieber said. "I take all my friendships with people of all cultures very seriously and I apologise for offending or hurting anyone with my childish and inexcusable behaviour

British tabloid newspaper The Sun first published the video on their website.

In it, a then 15-year-old Bieber tells a joke about black people that has a racial slur as the punchline.

Before he says it, someone warns him not to - but he says the offensive word anyway amid laughter.