The claws are out between charttopping hitmakers Lily Allen and Katy Perry.

The acid-tongued Allen is going for Katy’s throat after claiming the “I Kissed A Girl” star is a swagger jacker who once called her fat.

“I happen to know for a fact that she was an American version of me,” Lily fumed in a British radio interview last week.

“She was signed by my label in America as, ‘We need to find something controversial and kooky like Lily Allen.’ And then they found her.”

‘I think the lyrics and stuff are a bit crass,” she added

Lily says she’s angry over a string of supposed fat jibes Katy has made about her frame:

“When I met her I was bit frosty with her because someone asked her to describe herself. She’s like, ‘Aha, I’m like a fatter version of Amy Winehouse and a skinner version of Lily Allen!”

“It’s like, you’re not English and you don’t write your own songs, shut up!”

Lily Allen releases her new album It’s Not Me, It’s You on February 9.