According to its writer-director Andy Humphries, Sex Lives Of The Potato Men is "Dumb And Dumber meets Confessions Of A Window Cleaner". It sounds awful, and it is. Aimlessly charting the misadventures of four delivery men and their never-ending quest to sow their oats, it's as subtle as a copy of Viz and as witty as a graffiti-strewn toilet. Even a cast culled from popular BBC sitcoms can't raise a titter in a farce so relentlessly coarse it makes Bernard Manning look like Oscar Wilde.

When we first meet Brummie spud distributor Dave (Johnny Vegas), he's being thrown out of the house by a wife understandably tired of his slobbish, drunken ways. Shacking up with compulsive masturbator Tolly (Dominic Coleman), Dave dedicates himself to a life of "fanny, blow jobs, big tits, and beer". But like his co-driver Ferris (Mackenzie Crook), a divorcee obliged to swap sexual favours for room-and-board at his former mother-in-law's, he soon realises the single life isn't all it's cracked up to be.

"EMBARRASSINGLY PUERILE"

British cinema has a long tradition of saucy sex farces, from the Carry On and Confessions... movies to such soft-porn favourites as Come Play With Me. Potato Men, however, belongs to a more recent and less noble tradition: the vulgar "grossout" farce produced by the Farrelly Brothers and their many imitators. Evidently believing that nothing succeeds like excess, Humphries assaults the viewer with an orgy of group sex, three-in-a-bed sessions, and sordid encounters behind a chip shop counter. The result would be unspeakably vile if it wasn't so embarrassingly puerile.

"The person I feel sorry for is me," says Dave in one of his typically self-absorbed moments. But the people who really deserve sympathy here are Lucy and Julia Davis, whose excellent work in TV series The Office and Human Remains will forever be sullied by their connection to this ghastly enterprise.