The man behind "American Idol," Simon Fuller, is suing nasty-man judge Simon Cowell in a dispute that could drive Cowell off the show.

Fuller, who created "Pop Idol" for British TV and brought it here as "American Idol," filed the suit after seeing a new talent-search show Cowell launched Saturday night in England called "X Factor."

Fuller claims the new show is a rip-off of the "Idol" format.

Cowell branded the claim "totally and utterly ridiculous."

But the falling-out between the two men most responsible for the phenomenal worldwide success of "Idol" has many people questioning whether Cowell will continue as a judge on "Idol" — or whether Fuller will want him — when the show returns early next year.

Cowell showed up last week for "Idol" auditions in Orlando — the show is currently holding try-outs for its fourth edition — a Fox spokesman said yesterday.

"We anticipate he will be at every audition and will be a part of the show," said the spokesman.

Cowell devised the "X Factor" and owns the show on which contestants compete in three categories: under-25 singers, over-25 singers and groups.

The acts from each category are whittled down to three — and will compete in a live final in December.

The twist on the "Idol" format is that the judges — Cowell, Sharon Osbourne (search) and Louis Walsh (search) — will each be responsible for coaching a category winner, putting their own prestige as musical kingmakers on the line.

The exact details about audience participation on "The X Factor" have not been disclosed. But it is believed that viewers will vote for winners in category finals and then the grand finale.

Plans for the new show have been known for months, but Fuller, the man behind the Spice Girls (search) and one of the most powerful figures in the music business, apparently waited until he saw the first show on Saturday before beginning legal action.

Fuller's company, 19 Productions (search), is reportedly to be preparing a video comparing elements of the two shows — including logo, music and camera angles — which it is planning to use as part of its legal action.

The video will highlight so-called similarities between the two shows — including having contestants bursting out of audition-room doors, either in tears or breathlessly happy, and being hugged by the show's host.

The collaboration between Cowell and Fuller has been one of the most successful in modern TV history — and both Simons have earned millions from the show.

All participants on "Idol" must sign contracts that obligate them to record for Cowell's BMG record label and be managed by Fuller's 19 Productions.

Fuller became the first British music manager since The Beatles' Brian Epstein (search) to hold the top three spots in the U.S. charts, with singles by artists from "American Idol."

Cowell is due to work as a judge on the two series of "American Idol."