Britney Spears performance on The X Factor was surrounded by bizarre behaviour from the troubled star, according to a newspaper report.

The Sun claims that Britney snubbed the show's contestants by rehearsing in private and not even watching them perform her songs.

And the paper also claims show supremo Simon Cowell, one of the most powerful men in the global music industry, was prevented from meeting the star in her dressing room by her minders.

The other judges, Cheryl Cole, Louis Walsh and Dannii Minogue, are said to have been forced to wait in a corridor to pose for a snap with the star.

She had earlier refused to use a Winnebago supplied at the studio and had been given Cowell's green room as a dressing room instead.

The Sun quoted a show insider as saying: "You have never seen so many heavies. Even around the judges' dressing rooms was sealed off by Britney's security people. When the judges went to meet her, her security wouldn't let anyone past."

And when Simon Cowell finally met Britney he was stunned to hear she hadn't watched the five remaining acts perform.

The insider said: "Everyone was stunned she admitted that she hadn't watched the show. There's a TV in the dressing room.

"Simon tried to have a conversation, but Britney was pretty vacant. In the end he just walked off."

Many viewers believe that the Britney mimed her new single Womanizer on the Saturday night show - but she didn't sing at all when she went on for the obligatory appearance at London's G.A.Y. club.

Around 1,500 fans sang for her and gave her a cake for her birthday on Tuesday, but unlike most visiting pop icons she refused to take to the stage.