The US Department of Justice is digging deeper into the alleged anti-competitive licensing practices of the recording industry trade group, the Recording Industry Association of America (RIAA), which led the legal crusade against music-swapping service, Napster.

The Justice Department invited several internet music ventures and startups to 'behind closed-door' discussions in Washington, according to reports.

Gina Talamona, a Justice Department spokeswoman, said: "The antitrust division is looking at potential anti-competitive practices and the competitive effects of certain joint ventures in the online music industry."

Early last week, the Justice Department served the RIAA with subpoenas as part of a widening investigation into alleged price-fixing and collusion in licensing online music.

The investigation will scrutinise the operations of the two online music services, MusicNet and Pressplay, supported by the record industry, as well as the licensing terms offered for access to the labels' libraries.

The antitrust division is also exploring allegations that the labels and the RIAA colluded to set higher prices charged to internet radio broadcasters.

"We are confident that, once it has gathered the relevant facts, the Department of Justice will conclude that our actions have been fully compliant with all applicable laws," RIAA spokeswoman Amy Weiss said in a statement.

"Indeed, the steps we have taken to facilitate the legitimate online marketplace have been pro-competitive and beneficial to the consumer."

"Our actions in the courts, the Congress, the Copyright Office and in licensing negotiations have sped the availability of music to consumers online and spurred the development of legitimate business models," Weiss added.

The pace of the investigation has intensified as the new label-backed subscription music services plan to launch next month.

Several state attorneys general are also watching for signs of anti-competitive behaviour.