Miley Cyrus thinks Justin Bieber should be allowed to ''grow up''.

The 21-year-old pop star has defended her pal, who was recently at the centre controversy when videos emerged of him telling racist jokes as a teenager, and thinks it's difficult for him to develop and make mistakes because he's in the spotlight.

Appearing on Australia's 'Today' show, she said: ''I think people should have time to grow up and figure out who they are.

''I think people need to sit and think of the times in their lives they were not proud of who they were.

''Imagine if that was completely exploited and everyone had their opinions.''

Justin was recently forced to apologise after clips emerged of him using the N-word and joking about joining the Ku Klux Klan at the age of 14.

He said: ''At the end of the day I just need to step up and own what I did.

''Facing my mistakes from years ago has been one of the hardest things I've ever dealt with.

''But I feel now that I need to take responsibility for those mistakes and not let them linger.''