Lindsay Lohan and Paris Hilton are embroiled in a foul-mouthed internet fight.

The pair - who were once friends - have been trading insults on popular social networking site Facebook. 'Mean Girls' star Lindsay branded the hotel heiress a "b***h" and "pathetic" before launching a four-letter tirade after Paris had set up a group on the site called 'Firecrotch', referring to the actress' red hair.

But Paris hit back, saying it was her who was the pathetic one because she has set up a Facebook group about her first called 'Paris Wets Herself', which refers to a couple of incidents where the 27-year-old blonde is said to have urinated in a sauna and in the back of a taxi cab.

The former friends initially fell out over Greek shipping heir Stavros Niarchos III, who they have both dated. Lindsay, 23, is now openly gay and dating DJ Samantha Ronson, 31, while Paris is in a relationship with Good Charlotte guitarist Benji Madden.