UK users of a hugely popular music download site based in Russia have been told they are breaking the law.

AllofMP3.com , is a Moscow-based service that undercuts legal sites by enormous margins. For example a British shopper can download an album from iTunes Music Store for around £9.79. However if they use AllofMP3 a typical charge for an album is about £0.75.

This is because AllofMP3 prices its downloads by file size. The music industry also said the prices are cheaper because the site doesn't pay royalties to copyright owners. Another attraction to this price differential, the catalogue of music on the site is enormous and even includes Beatles albums that Apple is not allowed to sell.

Recent figures from market research firm XTN Data suggest that AllofMP3's market share, is second only to iTunes, and has a 44 per cent share of the UK market.

That puts it ahead of Napster with eight per cent, and Wippit and MSN both with six per cent of digital music sales in the UK.

The site has is a thorn in the side of the international music industry which has been gunning for it for quite some time. The website is run by a Russian company, MediaServices.

It claims everything is licensed by the Russian Multimedia and Internet Society (ROMS) and the Rightholders Federation for Collective Copyright Management of Works Used Interactively (FAIR). It says it pays licence fees " subject to the Law of the Russian Federation" and can't be held responsible for the actions of foreign users.

The statement on the site warns users they may "not able to download audio and video from AllOFMP3.com if is (sic) in conflict with the laws of your country of residence."

However the IFPI said is ripping off musicians. The organisation which represents the recording industry worldwide, including Russia is adamant AllofMP3 s not a legal service either in Russia or anywhere else and is not paying artists or copyright holders.

Two separate criminal proceedings are ongoing in Russia. The public prosecutor in Moscow is taking a former director of MediaServices to trial. And a second case against a current director of MediaServices is in the investigation phase.

A spokesman for the IFPI said Russia is known to be notoriously poor in enforcing intellectual property rights (IPR). He said these cases will prove " the acid test" to see if the country will now protect IPR.

However, British consumers who buy music from an unlicensed site are infringing copyright. In theory, they could be sued by the music industry. The IFPI said that at the moment it was concentrating on stopping AllofMP3 from trading. But it wouldn't rule out taking legal action against consumers.

"We have options to pursue legal action in some countries," a representative told Computeractive.

The IFPI would not however comment on which countries. However people in the UK should be aware they would be infringing UK copyright laws by using the site. This could leave them open to charges under UK copyright legislation. People have already faced charges for using file sharing sites under the law.

The IFPI is also hoping the credit card industry will help to clamp down and stop payments to this site.