In an interview for this week's Radio Times, Louis claimed: "She thinks she’s a bigger star than she actually is.”
He explained: "She is a bit rough round the edges and when they announced she was on the panel I was expecting a chav in a tracksuit — which is what we got. But she’s a lot of fun.”
The Irish music mogul also confessed that the series has suffered without Simon, who quit the show along with Cheryl and Dannii back in 2010.
He said: “It’s suffered without Simon — it’s like the Rolling Stones without Mick Jagger.
“Last year Tulisa and Gary were thrown in at the deep end and we struggled a bit but this year they're stronger.”
Louis also revealed that he aimed to stay on the show for at least ten years, but was unsure of sticking around after that.
"My ambition’s to get to 10 years. After that we’ll see," he commented. “I don't want to be like Brucie. I’ll know when it’s time to give it up.”