Pop superstar Lady GaGa has launched a crackdown on her fan website amid allegations of bullying.

The Poker Face singer set up her own social forum, Littlemonsters.com, so her fans could converse in a safe online environment, and she was shocked when one user complained other members were making fun of her on the website.

The female fan wrote in a post on the site, "Why are some people that are supposed to be promoting online kindness constantly at me (sic)?!... I can't even post what I feel on here anymore without being constantly put down! I actually can't stop crying... I've blocked people who are at me but they don't stop what am I supposed to do..."

The post prompted a swift reaction from Gaga, who vowed to launch a investigation and hunt down any bullies using her website.

She writes, "Don't worry okay we're all here for you! And I'll make sure the site looks even deeper for any bullies!"

The singer also runs anti-bullying charity The Born This Way Foundation.