American Idol judge Randy Jackson says he is “shocked” by Simon Cowell’s decision to quit the show.

The TV star described it as a “bizarre” move that summed up the unpredictable nature of the US singing contest.

“I was shocked. I knew he was working on his contract and doing things, but it’s just so wild – this show is just so unpredictable,” he said.

Jackson, 53, was asked about Cowell’s announcement during an interview with chatshow host Ellen DeGeneres – a fellow judge on the Idol panel.

He said he knew the music mogul had been discussing his contract – but had no warning of the consequences.

“I’ve been doing this show for nine seasons and the two words I’m really leery of right now are ‘contract negotiations’,” he said. “You never know what that means or where it’s going to go.”

But he added: “There have been so many ups and downs this season and I can’t believe it – it’s just so bizarre.

“Ryan [Seacrest] and I were just talking about it yesterday and we were like, ‘It’s such a wild show, such a ride.’”

Cowell, 50, is leaving American Idol when the current series ends to concentrate on launching the US version of X-Factor.

Ellen DeGeneres showed off her more cut-throat side during her second appearance as a judge on American Idol.

The US chat show host had a say in eliminating hopefuls as the Idol judges cut yet even more contestants from the competition during Hollywood audition week.

The remaining would-be pop stars were put into groups by the show’s producers and had to perform on stage together in front of DeGeneres, Simon Cowell, Kara DioGuardi and Randy Jackson.

And it was DeGeneres who appeared to be the most cutting with her comments, criticising one group’s style of performance.

“It really was weird. You’re dressed like Cirque Du Soleil in all these outfits, it was surreal,” DeGeneres critiqued about one group who called themselves Neopolitan.

But despite her criticism of their performance she put the group through to the next round.

All told, 181 finalists were trimmed down to 12 guys and 12 girls in this week’s auditions.

The show then returns to its live format, where viewers get the chance to vote for their favourites.