ottawa-Pop singer Justin Bieber has come under fire after a video has emerged of him using the the N-word in a racist joke.

The footage, which was exclusively obtained by The Sun, shows the 20-year-old grinning while using the highly offensive term in an attempt to make his friends laugh.

Justin, who appears to be a number of years younger in the video, can be heard asking his friends ‘Why are black people afraid of chainsaws?’ Justin, whose mentor Usher is African American, then started making the noise of the chainsaw  and concluded his ‘joke’ with ‘ Run. It’s thought the video, which sees one pal beg him not to say the punchline, has been around for some time but his camp have been keen to keep it underwraps.

A source told The Sun: ‘This video is Justin Bieber and his camp’s worst nightmare. Even after the year he’s had - when he’s never been far from controversy, this tops the lot.

‘Justin has been taken under his wing by some of the best in the industry and they won’t stand by him after this.

This will be a real kick in the teeth - showing his true colours on film.’

Justin is of course signed to Usher Raymonfs label RBMG Records and throughout his career he has worked closely alongside numerous African Americans including will I am, Big Sean and Lil Wayne. He also has a close relationship with Jaden Smith and his father Will, who has been supportive when he has been involved in various scandals. Last year the multimillion selling artist revealed that he took weekly phone calls from his ‘mentor’ Will.

In an interview with the Hollywood Reporter magazine, Bieber said Smith and he have counselling sessions and discuss ‘any potential issues, emotional or otherwise.’ He has also been known to stand up against racism in the past and when someone critiszed his choice of friends, he wrote: ‘It’s not your place to judge, God put these people in my life for a reason, and just because theyare African - American that makes them bad people?

‘These are people that I love and all of us are going to help make the world a better place.’ At the start of this year Justin was arrested for drunk driving and resisting arrest while allegedly drag racing in Miami. A month afterwards he was accused of abusing a flight attendant on a private jet until she was forced to hide in the cockpit.

The troubled teen singer and his entourage were also said to have smoked so much marijuana on the flight between Canada and New Jersey that the pilots were forced to wear oxygen masks. A spokesperson for Justin has been contacted for comment.