The two duked it out on the micro-blogging site after Perez wrote a post (er, "Tweet") letting it be known that Allen was casting for her new video, and that he should be considered for a role in the clip.

The quick-witted Brit fired back — writing "Oh, I'm sorry, we've already cast the jealous and bitter lonely old queen role. Next time, eh?"

"Jealous of who?" Hilton responded. "David Beckham, maybe. And if I wanted to be a f---ed up Brit, I'd rather be Amy Winehouse — whose [sic] got talent."

The two then exchanged "you're so obsessed" barbs, before Hilton decided to take the beef to the next level, taking a potshot at the sales of Allen's just-released album, It's Not Me, It's You, which is selling at a low retail price.

"Congrats on your album doing well in America, though," he wrote. "It's REALLY HARD to sell copies when u discount it to $3.99. Desperate."

"It's also #1 everywhere else in the world, douchebag," Allen replied. "Go away you little parasite."

Hilton then tried to play nice — saying that both he and Allen were "big fat c---s," and that's why he loves her — then abruptly switched gears, getting catty about ads Allen's label had purchased to run on his Web site.

"P.S. Thanks for advertising on my website," Hilton wrote. "I'll take your money (or the label's) anytime!"

"I know you will, and that's what makes you a cheap ass w---e," Allen responded. "Now leave me alone, stop following me, I'm working. Bye x x."

Mike Skinner, who performs as The Streets, used his blog on the site to respond to Allen's claim that his music was boring. "At least she's not stalking me anymore," he wrote.