Napster has launched the world's largest MP3 store with tracks now compatible with the iPod and iPhone.

The new download store is more than 50 per cent larger than any other MP3 store, according to the company, and all sales in the US will be in the DRM-free MP3 format.

Napster's new shop is in direct competition with Apple's market leading iTunes store and will offer a larger number of songs without copy protection or digital rights management than its competitors.

Visitors to the store can subscribe to Napster's on demand streaming subscription service, which is web-based with no need to download software.

Chris Gorog, chief executive of Napster, said that music fans want to find both major label artists and independent music all in one place.

"Our new MP3 store, together with our award-winning all-you-can-eat music subscription service, provides the most comprehensive and exciting music experience available," added Mr Gorog.

Napster created a stir of controversy in its early existence as a peer-to-peer file sharing network when Metallica found that its entire back catalog was freely available on the site and filed a copyright infringement lawsuit against the company.