Britney Spears has been given a public boost by her teenage sweetheart Justin Timberlake.

As the troubled pop star fights for custody of her two young sons and attempts to salvage her career amid allegations of eating disorders and drug use, her famous ex has come to her defence in a new TV interview.

Timberlake appeared on Wednesday's Oprah show in America, where he agreed to discuss something he rarely talks about - his ex-girlfriend.

The awkward pop singer, choosing his words carefully, said, "I haven't spoken to her in years. I mean, there's no ill will - I have nothing but love for her."

"We dated each other at a time... We were teenagers, you know?"

Asked to comment on Spears' public problems, her ex added, "I think she's a great person, and I don't know her as well as I did. What I do know about her is she has a huge heart."