A judge in the US has thrown out a case brought by writers claiming studios and TV executives in Hollywood discriminate against those over 40.

District Court Judge Charles W McCoy said some of the alleged discrimination was within the limits of the law.

He said the 175 writers involved in the case would have to prove the discrimination on an individual basis.

This means the writers could refile their cases individually.

"We consider this a bump in the road," said Paul Sprenger, the lead attorney representing the writers.

"Sometimes these things take years and it should be perfectly obvious to the courts that this is a meritorious claim."

He said the writers did not plan to present their cases one by one, but may appeal or launch a class action claim.

'Broad-based claim'

The legal case was originally filed in the Los Angeles District Court and related to alleged discrimination that goes back to the 1980s.

The case was launched against six television companies - which included CBS, NBC, ABC and Fox - 11 production companies, and talent agencies.

The case alleged infringements of the federal Age Discrimination in Employment Act, the Labor Management Relations Act and the California Fair Employment and Housing Act.

The federal court had said they were not able to bring forward a group claim, so the writers refiled the case in a state court.

"We are pleased the court has decided that these television writers cannot proceed on such a broad-based claim," a CBS statement stated.

"We are also confident that any individual claims of discrimination will be shown to have no merit."