Justin Bieber was bullied as a child.

The 18-year-old heartthrob - who has leant his single 'Born to Be Somebody' to a US documentary on school bullying - admits he fell victim to tormentors before becoming famous.

He said: ''I was bullied. Most people in their lifetime have been bullied at some point. I think that it's about time that people start making a change.

The film, titled 'Bully', looks at the issue through the eyes of five youngsters, and the 'Boyfriend' hitmaker believes it has the potential to make a real difference.

He told 'Showbiz Tonight': ''A lot of the time, principals let it go, or teachers let it go, or other students just let it go, but I think this movie's really powerful and can help change a lot of lives.''

Meanwhile, he urges those who witness bullying, as well as those who experience it first-hand, to share the problem with someone and seek help.

He said: ''If you're a bystander, too, tell somebody - because a lot of times, it's just not spoken of, and you ended up - you end up keeping it all inside, and then it just hurts even more.''