Napster, a system which enables users to swap music files free over the internet, was recently ordered to filter out all copyrighted material by an American court.

While the company claims it has been doing so, the Recording Industry Association of America complained on Tuesday that it found no evidence of compliance.

On Wednesday, Metallica's lawyer said that the group had also filed a complaint with the US District Court in San Francisco that Napster has failed to block access to its music as ordered.

Copyright

Lawyer Howard King said Judge Marilyn Hall Patel, author of the 5 March injunction against Napster, had issued an identical injunction in the separate case taken by Metallica and hip-hop performer Dr Dre.

Under the injunction issued by Judge Patel, Napster must block copyrighted songs as identified by the record companies which filed the copyright infringement suit in December 1999.

Napster recently claimed more than 275,000 songs can no longer be downloaded from the system, and that nearly a third of its staff were working on complying with the court order.

Napster chief executive Hank Barry issued a statement rejecting the RIAA's criticisms as "an attempt to change the subject rather than co-operate with Napster as the injunction specifies".

Heavy rock