Troubled pop star Justin Bieber is at the centre of another scandal after footage allegedly showing him making a racist joke was leaked to the press.

The clip, obtained by editors at Britain's The Sun on Sunday newspaper, is said to have been shot during the production of his 2011 documentary Never Say Never.

In the short video, Bieber appears to ask pals, "Why are black people afraid of chainsaws?"

Grinning, he then adds, "Run, n**ger, n**ger, n**ger, n**ger, run."

It is the latest blow to the singer, who counts prominent African Americans including Usher and rapper Lil Wayne among his celebrity friends, amid a storm of legal troubles.

The Baby hitmaker, 20, will appear in court in July (14) to face charges of Dui, resisting arrest without violence and driving with an expired licence following his arrest in Miami, Florida earlier this year (14).

He is also facing prosecution in Toronto, Canada, where he is accused of involvement in the alleged assault of a limousine driver during a night out in December (13).