Playwrights Andrew McCarten and Stephen Sinclair have filed a suit for �180m in Los Angeles saying scenes in the movie, about a group of Sheffield men who turn to stripping, mirror their play Ladies Night, which toured in Britain and New Zealand.

The legal action comes just three weeks before the US Academy Awards at which the film has been nominated for four Oscars.

Cheeky definitely, but the film has become a phenomenon

Full Monty producer Uberto Pasolini has denied his film is a rip-off, saying it was "wholly, completely original" and that no one connected with it had seen Ladies Night.

Already the biggest grossing British film of all time, the video version of The Full Monty, which went on sale earlier this week, is also tipped to become an all-time best seller.

The playwrights' case alleges that the scenario of The Full Monty borrows heavily from their 1987 play, which was New Zealand's most successful theatrical production.

They say it also features unemployed northerners stripping to earn money, the realisation they could only beat professional troupes by baring all and similar characterisations.

The writers are seeking damages from the film's distributor, its maker 20th Century Fox, Redwave Films, director Peter Cattaneo and screenwriter Simon Beaufoy.

The suit has been lodged at a crucial stage in the film's Oscar race, with nominations for best picture, best original screenplay, best director and best original music at stake.

However, it is not the first allegation of plagiarism against the film which has taken more than �120m at the box office.

If successful, the writers could strip all profits from the film

West London film maker Paul Bucknor claims it bears a marked similarity to his own outline for Satisfaction, although that had more black characters.

Mr Bucknor signed a deal with Mr Pasolini, but the producer has said though they discussed the idea, the final story was his.

One of The Full Monty's rivals for best film Oscar is Amistad, Steven Spielberg's historical film of a rebel slave ship, which has also faced a plagiarism suit.

'Feel good' factor

Video retailers reported "unprecedented" sales of the video at shops around the country as fans rushed out in the first two days of its release to own the "feel good" film for themselves.

"We were selling 3,000 copies an hour and it is still selling strongly today," an HMV spokesman said.

"Although it has been a great success at the cinema box office, many people still have not seen it and it is the perfect purchase for television viewing.

"By the end of the week we estimate that Fox will have sold one million copies."

The film's distributors, Entertainment UK, predicted The Full Monty would topple Independence Day as Britain's best selling feature film video within a week.

"We are working round the clock to make sure supply meets such phenomenal demand," spokesman Paul Ludlum said.

However, Doug Hopper, market researcher for the British Video Association, urged caution in declaring The Full Monty the all time top seller too soon.

Single video releases Ghost and Jurassic Park had both achieved about 1.6m sales, he said.