Britney Spears reportedly walked out of US 'x factor' when she unhappy with one contestant.

The blonde beauty and fellow panellists L.A. Reid, Demi Lovato and Louis Walsh - who was filling in for ill Simon Cowell - ''didn't want to waste their time'' when a wannabe in Kansas City attempted to audition with his back to the judges.

An eyewitness told People.com: ''It was really awkward. You could tell the judges were done. I don't think they had a choice. They didn't want to waste their time.''

Another source explained: ''He was one of the worst singers and had a bad attitude ... [The judges] all hated it and walked off.''

L.A., Demi and Louis all then made their way back to their judges' seats to hear the last contestant apart from Britney, who eventually returned for another batch of wannabes.

The episode comes just weeks after Britney made her judging debut on the show in May.