Louis Walsh has branded Cheryl Fernandez-Versini "lazy" and "irrelevant" in a personal attack on his X Factor colleague.
Walsh - who has reportedly been dropped as an X Factor judge - told Heat magazine: “Cheryl wasn’t great last year. She’s sometimes lazy and lacks energy.
“She needs to give more, she can give so much more. She’s irrelevant these days.”
“I know people say the same about me, but apart from anything, I am fun and I have a rapport with Simon [Cowell].”
But the former Girls Aloud star hit back at Walsh, telling her 5.47 million Twitter followers that Walsh "has some kind of an obsession" with her.
She added: I mean this is every year whether I am or am not a part of the show and btw this is the same man asking me what he should say to contestants on our way to the stage because 'he doesn't know'."
Simon Cowell is reportedly planning a shake-up of the show in a bid to boost ratings.
"Louis Walsh is one of the good guys. We will always be friends. The door remains open and who knows what's next," he wrote.
One Direction's Louis Tomlinson, DJ Nick Grimshaw and Robbie Williams have all been tipped as potential replacements for Walsh, who has been a judge on the show since it was launched in 2004.