Cowell appeared on Pop Idol and American Idol before X Factor

Mr Fuller claims Mr Cowell's ITV1 show X Factor copies his Pop Idol format.

Mr Fuller's company 19 TV, which created Pop Idol and American Idol, is taking action against FremantleMedia, Cowell and his firms Simco and Syco.

Mr Cowell, who became a household name as a Pop Idol judge in 2001, called the claim "utterly ridiculous". The case is due to resume at a date to be fixed.

'Contract breach'

As well as claiming breach of copyright, 19 TV is suing for breach of contract because it alleges some of The X Factor's production team also worked on Pop Idol after signing contracts which prevented them from working on rival shows.

Neither Mr Cowell nor Mr Fuller were at London's High Court on Wednesday, when lawyers from both sides addressed the judge before the case was adjourned.

Pop Idol attracted 12 million viewers for the final of its second series in December 2003.

Simon Fuller was the man behind the Spice Girls and S Club 7

Mr Cowell subsequently became a judge in the show's hit US spin-off, American Idol, which spawned pop star Kelly Clarkson.

The X Factor began on ITV in September 2004, and sees pop wannabes face Cowell and fellow judges Sharon Osbourne and Louis Walsh.

The first episode of the second series drew an average of 7.5 million viewers in October this year.

Simon Fuller, who runs management and media company 19, was the man behind successful pop acts such as the Spice Girls and S Club 7 before creating Pop Idol.