Cat is about to return to UK screens on Sky 1's 'Sing: Ultimate A Capella', a singing contest which focuses on a capella groups and raw vocal talent.
It has inevitably attracted comparisons to rival formats, and Cat recently suggested that The X Factor is in need of a rest.
"I think every big show like that is cyclical, like Britain’s Got Talent or America’s Got Talent," she said.
"They are hugely successful and then people get bored, and then they put them away for a bit, then they miss them, then they bring them back."
Always one to defend the show that he has judged for thirteen years, Louis has now hit back at Cat's comments.
Speaking to The Mirror, the Irishman claimed Cat is "jealous" that she doesn't have X Factor frontman Dermot O'Leary's job - and had his own dig at Sky 1's ratings.
"I think the truth is that Cat would love to be hosting the show, but we have already got Dermot and he is the best in the business," Louis sniped.
"She can stay on Sky 1 where nobody is watching. It is a bit of the green-eyed monster from Cat. Sorry Cat, we don’t need you."
While Cat may not have a primetime Saturday night gig in the UK, she has succeeded where many British TV stars have failed by cracking America.
She has been the host of FOX's So You Think You Can Dance? since 2005, and recently fronted a US version of ITV gameshow Big Star's Little Star.
Earlier this year she made a minor UK comeback when she starred as the mysterious Maskface in 'The Missing Crown Jewels' segment on Ant and Dec's Saturday Night Takeaway.
Cat is expected to reunite with her former SM:TV Live co-hosts again next year on a 20th anniversary special of the classic kids' show.