Perry 'vows to be as severe as Cowell'

Katy Perry has claimed that she is going to be merciless as a guest judge on American Idol.

The 'I Kissed A Girl' singer said that she is not planning to give contestants a "pity-pass" and insisted that her criticisms will be as severe as Simon Cowell's, Angry Ape reports.

Perry wrote on her Twitter page: "Ok, I must confess, I'm SO excited to guest host on American Idol. I think Simon & I are gonna get along famously. He tells it like it is... & truthfully, that's how ppl need to hear it.

"This isn't like ur local high school talent contest. This is AI! Ppl that wanna b in music biz need to know this sh** isn't a cake walk! :P (sic)."

She added: "No more pity passing kids on to the next level just cause they have some kinda sob story or cuz they look like a replica of past Idol winners (is it me or does every year have like the nerd, the rocker chick, gospel chick, etc.)

"Anyway, I'm just excited to tell it like it is & high 5 Simon all day. He may be devil of judges but he's riggght."