PASADENA, California (AP) — Simon Cowell, the acerbic Brit who has helped give American Idol some of its sharpest — and nastiest — moments, will leave the hit TV singing contest after this season.

The cantankerous judge said Monday that The X Factor, a talent show he created and which is popular in Britain, will join Fox’s schedule next year. Cowell will be a judge on The X Factor and its executive producer.

Cowell’s decision is the biggest threat yet to what has consistently been the country’s top-rated TV programme and a true cultural force. This season, original host Paula Abdul has been replaced by Ellen DeGeneres.

But Cowell, with his caustic commentary, has long been seen as the big star of Idol.

He said it would have been difficult for him to do both shows. While he makes a reported $36 million a year to be on American Idol, he owns The X Factor and could make much more if the show takes off.

Ironically, The X Factor led to a lawsuit several years ago between Cowell and American Idol creator Simon Fuller, who alleged that Cowell copied the format for the British version of The X Factor from the original British Idol. The suit was settled amicably.

Cowell and top Fox executives made the announcement to reporters in Pasadena at a meeting of the Television Critics Association; they said they had reached an agreement only a few hours before.

“I was offered a lot of money to stay on,” Cowell said. “But that wasn’t the reason behind it. I wanted to do something different. I wanted a new challenge.”

But an even greater challenge is posed for Idol producers. Without the show’s biggest attraction and most critical judge, will American Idol lose steam and plunge even more in ratings? At least one analyst, Shari Anne Brill of Carat USA, said the Idol audience probably will decline next season.

“I think it’s that brand of sarcasm combined with professional know-how that makes Simon the audience magnet that he is,” she said. “I really believe the show revolves around him. He’s the linchpin of the show’s success. He has tremendous influence on how the audience votes. He’s interesting to listen to. He’s brutally honest.”

That said, even without Simon, she predicts the show “will still be a formidable player on Fox’s schedule”.