The public feud between 23-year-old "Smile" singer Allen and "I Kissed a Girl" girl Katy Perry, 24, is heating up after the two warbling divas called each other "fat" and "crass," respectively. 

Now Allen has upped the stakes, threatening to publish Perry's private mobile phone number on the Internet, the Sun reports.

"I have Katy Perry's number, someone did me a favor," Allen writes on her Facebook page. "I'm just waiting for her to open her mouth one more time then it hits Facebook."

Hmm; someone did her a favor? Someone call Scotland Yard, because it's nearly impossible to think of  a person who might want to publicly humiliate Katy Perry these days.

Lily has further fanned the flames of animosity by joining two anti-Perry Facebook groups, "I hate Katy Perry and her dumb-ass song I Kissed A Girl" and "Katy Perry? Who in the hell does she think she is?"

Oooooh; that will show mean old Katy Perry!

Cripes; with the company Lily Allen's been keeping lately, one would think that she'd be able to act a little more mature.