The director Mike Leigh has hit out at an obsession with scripts which he says is cramping British film and hamstringing young talent.

Leigh, the creator of such masterpieces as Secrets and Lies and High Hopes, whose tragicomic stories grow out of rehearsals with actors, lambasted the film establishment for their mania for judging projects on "bits of paper" that have little or nothing to do with the finished film.

He accused the producers and public bodies which set the strictures on which film would be funded of not understanding what happened behind the camera.

"Scripts as such are nothing to do with the film," he said. "The script process is a bureaucratic thing that gets in the way of films being made, because the people who fund films have not the wit, the imagination nor sophistication to find other ways or giving out the dosh without going through this devaluing, philistine nonsense."

Leigh argued that "the fundamental problem" was that organisations that funded films "don't get" that movies were only made when the cameras started to roll and afterwards in the editing room.

"You have to deal with people who don't get it, and are bound by the notion of a script. Worse than that, they somehow think that a script some way simulates a film.

"All scripts, if we are honest, are just hieroglyphs on a piece of paper that merely put down something more than you needed to - or you wanted to - put down in the first place," he said.

Having been unable to make a movie himself for the 17 years between Bleak Moments and High Hopes, Leigh said he sympathised with young film-makers being forced into ever smaller slots for their shorts.

"It is irresponsible, eccentric and very depressing", he said, that British shorts were being corralled into three or 10 minute gaps in the schedules, while French shorts were often half an hour long.

His comments, at the Orange Short Film Masterclass at the London Film Festival, will be taken as a thinly-veiled attack on the Film Council, which was founded last year vowing to make sure that all scripts it backed were fully developed before they were deemed fit to be made.

Indeed one of its leading members, the producer Dun can Kenworthy, the man behind Notting Hill, is fond of stressing how Richard Curtis had to rewrite Four Weddings and a Funeral 17 times.

Leigh did not mention the Film Council by name, but he wondered aloud whether the sort of films that made his name with might get off the ground now.

More improvised ways of working with actors were now common everywhere, with scripts often only used for the barest guidance. "It is not that this method, as it was when I started, is a really unusual or rarefied thing," he said. He had two words of advice for the film-makers left out in the cold: "Never surrender."

Robert Jones, the head of the Film Council's Premiere Fund, which is set to back Leigh's next film, said he did not dispute the criticism. "I'm afraid I'm going to have to agree with him, particularly with the sort of film that he or other auteurs like Lynne Ramsay tend to make.

"It is also true of all films that there is a point where you can go over the script so often that it gets overcooked and it loses what attracted you to it in the first place.

"Scripts are at best a blueprint - we all know that, just like the shoots, they are only part of the process.

"But I would not take his argument as a reason not to pay for proper development. There are many ways to bake a cake."

'There are many ways to bake a cake'

Secrets and Lies

Few recent British films are as loved and admired internationally as Mike Leigh's 1996 film, which starred Brenda Blethyn and Timothy Spall, and told of the trials and tribulations of a south London family. Leigh has always been secretive about the precise methods he uses in his films. What we do know is that he never starts with a conventional script, instead preferring to work with his actors and develop their characters until a story improvised from rehearsals, and sometimes even a script, finally emerges.

Four Weddings and a Funeral

This film, which opened the floodgates for other recent commercial British hits, is entirely different. Written by Richard "Blackadder" Curtis, it went through an estimated 17 drafts before shooting began, and even then Curtis was on hand to tweak bits that did not seem to work. The producer, Duncan Kenworthy, is a firm believer in testing the script every step of the way.

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