Sharon Osbourne is delighted Britney Spears wasn't the "train wreck" some people were expecting when she appeared as a judge on The X Factor USA this season.

When Spears signed up to star on the hit TV talent show alongside Simon Cowell, Demi Lovato and L.A. Reid, many critics were quick to assume that the international songstress would fail to deliver.

Speaking to Heat magazine, Osbourne defended the singer - who famously had a very public breakdown in 2007.

The reality TV star and presenter explained: "People thought she was going to be a train wreck and she's not. She's a very nice girl - and she's had a hell of a tough time.

She added: "All she has ever really done is work and make money for people. Now, she's come to the age where she can take control of her life."

Osbourne also spoke about her relationship with music mogul Cowell - who was the person behind Spears' signing to the show.

She smiled: "Believe me, if I wasn't friends with him I wouldn't be here now! I can say anything I like to Simon. But if anybody else does? That's not allowed! I've gone past the ten-year mark with Simon, so I'm OK."