The film industry's undervaluing ofthe work of screenwriters - and the need for writers to be more assertive and proactive in response- were the recurring themes on the first day of this year's International Screenwriters Festival.

During an entertaining interviewat the Cheltenham event about the psychology of screenwriters The Pianist and The Diving Bell And The Butterfly writer Ronald Harwood drew the strongest positive reaction of the day from conference delegates when he attacked the director's possessory credit.

'It's appalling,' he said.

'Directors have an inclination to sweep away the writer, to pretend there isn't a script. It's disgraceful and the media buy into it. When The Diving Bell And The Butterfly was shown at Cannes there was a review on [UK television programme] Newsnight.

'They mentioned everybody except the writer. As it was my conception, I felt hard done by. It's not to do with me. It's the way the industry is organised.'

Speaking earlier in the day on 10 Producers Secrets Writers Need To Know, Stephen Woolley encouraged writers to listen to producers but warned, 'Writers can often fall into the trap of being a pawn in the process of making a film.

They can get the midnight call from producers: 'Don't make those changes!' And in a meeting the next day, they are caught like a rabbit in the headlights.'

Meanwhile, in a later session for writers entitled How To Be Good, script developer Kate Leys argued that in the film industry, 'People are frightened a lot of the time. People who are frightened tend to behave badly, or wildly. That's one reason why film meetings are often so baffling.'

It is in response to concerns like these that The Writers Guild of Great Britain has developed Writing Film, a set of guidelines for screenwriters and those working with them in the film industry, launched at the festival on Tuesday.

Screenwriter and chair of the Writers Guild of Great Britain film committee Olivia Hetreed, told delegates the guidelines, issued as a working document are designed to address issues raised at the two previous festivals 'to try to get from the current situation where there is a quite elderly Pact Writers Guild contract [dating from 1992] and very little appetite on the part of producers to renegotiate - when we started this process - that contract.'

Writing film comprises both guidelines on good practice and suggestions about contractual terms, in particular in relation to rights signed away by writers and the removal of writers from projects. The Guild is seeking feedback from the industry, Hetreed said.

The day ended with director Mike Leigh in conversation with producer Simon Relph. Leigh is famous for his improvisational approach to developing stories and not using conventional scripts. In a light-hearted comment on the advantages of his approach he said: 'I don't have some bastard hack telling me I can't touch his sacrosanct lines. And I don't have some bastard director touching my sacrosanct lines.'

The festival continues until July 3, with speakers including Julian Fellowes, Peter Kosminsky and controller of BBC Fiction, Jane Tranter.