London, Jan 6 :  Singer Lily Allen has started a feud with upcoming US singer Katy Perry.

There had been a strain in their relationship ever since Perry called Allen ‘fat’, reports thesun.co.uk. Now Allen is calling Perry ‘crass’ and is also threatening to post Perry’s number on the web.

Allen on her facebook page wrote: ‘I have Katy Perry’s number, someone did me a favour. I’m just waiting for her to open her mouth one more time then it hits Facebook.’

Allen also joined two groups. One is called ‘I hate Katy Perry and her dumb-ass song ‘I Kissed A Girl”. The other is ‘Katy Perry? Who in the hell does she think she is?’