Mobile phones with MP3 capability are outselling traditional CD players five-to-one and are now the most popular music devices in the U.K., according to figures released by the Entertainment Retailers Association (ERA) and compiled by market research organization GfK.

The analysis showed that in the 12 months ending September 2008, 32.1 million MP3 devices were sold in the U.K. The study found that 75% of these sales were mobile phones, although a large proportion of the devices would have been supplied free to mobile network customers as an upgrade under their contract terms.

Over the last two years, GfK reports that over 44 million mobiles with MP3 compatibility have been sold in the U.K. -- dwarfing the 8 million CD players sold over the same period. Approximately 90% of phones sold in the U.K. can now play MP3s.

"Never in the history of the music business have we seen a format take off like this before," said Russel Coultart, chairman of ERA Digital, ERA's special interest group for digital retailers. "There is now no doubt that MP3 is the fastest-growing music format of all time, faster than vinyl, cassette or CD."

ERA's MP3 Compatible campaign, which features a new consumer awareness logo for MP3-compatible products, was launched two weeks ago. Digital retailers including HMV.com, Play.com, 7digital.com, Tescodigital.com, Tunetribe.com, Woolworthsdownload.co.uk and Digitalstores.co.uk all now display the logo.

ERA is the U.K. trade body for recorded music, video, DVD and games, representing the interests of over 5,000 stores.