Singer Justin Bieber has apologised for using the N-word during the filming of a 2011 documentary "Never Say Never".

Bieber used the term when he was 17, but the documentary emerged recently, and Bieber had to issue a long apology for the racist remark, reports contactmusic.com.

The 20-year-old delivered an offensive punch line: "Run n*****, n*****, n*****, n*****, n*****".

In his apology, he has said: "As a kid, I didn't understand the power of certain words and how they can hurt. I thought it was okay to repeat hurtful words and jokes, but didn't realise at the time that it wasn't funny and that, in fact, my actions were continuing the ignorance."

"Thanks to friends and family I learned from my mistakes and grew up and apologized for those wrongs. Now that these mistakes from the past have become public I need to apologize again to all those I have offended."

Bieber, who is mentored by singer Usher, blamed it all on his immaturity.

"I apologise for offending or hurting anyone with my childish and inexcusable mistake. I was a kid then and I am a man now who knows my responsibility to the world and to not make that mistake again," Bieber said.

"Ignorance has no place in our society and I hope the sharing of my faults can prevent others from making the same mistake in the future. I thought long and hard about what I wanted to say but telling the truth is always what's right," added the "Baby" hitmaker.