In their latest file-swapping legal action, US film and recording industry associations have filed suit against MusicCity and others in a motion to restrain millions from trading copies of songs and movies online.

The Recording Industry Association of America (RIAA) and the Motion Picture Association of America filed suit against MusicCity, Grokster and Kazaa, which together form a network which the associations describe as a "21st century piratical bazaar where the unlawful exchange of protected materials takes place across the vast expanses of the internet".

The infringing digital files available on and through the defendants' network include illegal copies of hit sound recordings as well as recently released films, including many that are still playing in cinemas and are not yet legitimately available in any other media format, according to the complaint.

Similar lawsuits have been filed against Napster, Scour and Aimster.

Hilary Rosen, RIAA chief executive, said: "We cannot sit idly by while these services continue to operate illegally, especially at a time when new legitimate services are being launched."

Amsterdam-based FastTrack, also known as Consumer Empowerment, licenses its file swapping software to MusicCity and Grokster. FastTrack also manages Kazaa. While the three services provide user interfaces that differ cosmetically, users access the same network library.

The complaint also said that the defendants are aware of the illegal activity occurring on their system and "are capable of controlling the activities of their users and the infringing digital files available through their network".

MGM, Columbia Pictures, Disney Enterprises, Paramount Pictures, Time Warner, Twentieth Century Fox and Universal City Studios are among the companies listed as plaintiffs.

According to the RIAA, figures for the first half of 2001 showed that a count of singles on all media, including cassettes and CDs, dropped by 38.3 per cent in the US.