Each of these organisations has rules, and we have to live with them

Aaron Ryder, Memento executive producer

Nominations for the guild's awards will be announced on Thursday in Beverly Hills, California.

Victoria Riskin, president of the WGA West - which covers California - defended the decision, saying: "Our objective is to protect writers.

"But it's not easy when some wonderful screenwriting can't qualify. It always stirs up debate among the members when something like this happens."

While non-members are eligible for a WGA award, filmed need to be made under one of its contracts, or that of an overseas affliliate, to qualify for the honour.

In the Bedroom was written and directed by first-time feature film-maker Todd Field in 2001.

It has already been honoured by the National Board of Review, the Los Angeles Film Critics' Association and by the Golden Globes.

It is also considered a top contender for a number of Academy Awards nominations when they are announced on Tuesday.

'Proud'

Memento: A low budget thriller

Memento was written and directed by Christopher Nolan in 2000.

It has won awards from the American Film Institute and several broadcast critics groups. It was also nominated for a Golden Globe.

Aaron Ryder, an executive producer on Memento, said the WGA's decision was a shame but should be respected.

"Each of these guilds and organisations has rules, and we have to live with them," he said.

"It would have been great to get a Writers Guild nomination, or to win, but we're excited about the film's future, we're proud of our Golden Globe nomination and so we're not angry.''