A group of ladies from a North Yorkshire Women's Institute was the toast of the Cannes Film Festival today after the story of their famous naked calendar shoot was turned into a movie.

The film, Calendar Girls, is being given its first official screening on the French Riviera and is being hailed as the female Full Monty.

Starring Helen Mirren and Julie Walters, it tells how the middle-aged members of the Rylstone WI in the Yorkshire Dales posed nude for a charity calendar and became international stars.

Mirren and Walters were joined in Cannes today by Tricia Stewart and Angela Baker, the women on whom their characters are based.

Baker's husband John died of leukaemia five years ago and her best friend Stewart came up with the quirky fund-raising idea which cast off the WI's old-fashioned ''jam-making and Jerusalem'' image.

They hoped to sell a few hundred copies - instead they raised over half a million pounds for leukaemia research. Their remarkable tale has now been adapted for the big screen, and though the names have been changed - Rylstone is swapped for Knapely and the two main characters are called Chris and Annie - the essence of the story remains.

All the actresses, who include Celia Imrie, Linda Bassett, Annette Crosbie and Penelope Wilton - strip off for the film. But, like the real-life calendar, everything is tastefully done.

Director Nigel Cole said: ''This was a special film to make because we had an extraordinary true story to tell. ''It also demonstrates the breadth of talent of actresses over 40 who don't get the chance to show those talents in many films.

''They entered into the spirit of things very well and were incredibly brave - after all, this is a film about taking your clothes off.

''That might not seem such a big deal out here in the sunny South of France, but when you're doing it in the cold of Yorkshire it certainly is.''

Calendar Girls premieres in the UK in September with screenings in London, Leeds and Skipton.