By Breaking Celebrity News Staff

A singing slip-up on Thursday's episode of The X Factor caused outcry as millions of viewers heard contestant Leroy Bell singing before his microphone was even up to his mouth.

The blunder occurred while the finalists were performing a group number together, but still spawned speculation that the other performances could be faked, which Fox quickly addressed.

"All survival songs are performed live, with just a backing track," an X Factor representative said in a statement to TheWrap.com.

"For the group ensemble performance, the vocals are pre-recorded to allow acts to concentrate on preparing for their own live competitive performances on Wednesdays  - this is also no different to what other competition shows do for ensemble performances."

From Ashlee Simpson and Britney Spears to Milli Vanilli, numerous pop stars have been caught lip syncing over recent years but fans expect reality competitions to be more real than big budget stadium concerts and the mistake on Simon Cowell's new show has been slammed by fans online.