Key digital music retailers in the U.K. have joined together in support of a new campaign to increase consumer awareness about the MP3 format.

The home pages of seven companies -- 7digital.com, Digitalstores.co.uk, HMV.com, Play.com, Tescodigital.com, Tunetribe.com and Woolworthsdownload.co.uk -- now all display a new "MP3 compatible" logo to indicate that downloads sold on that site play on all PC and Apple Macintosh computers, and virtually every digital music player available.

The logo will also make it easier for people to identify legitimate download sites.

ERA Digital, the digital arm of the U.K.'s Entertainment Retailers Association (ERA), is behind the initiative. CEO Russel Coultart said in a statement: "2008 has been the breakthrough year for legal MP3 downloads. We now want to take the message out to music fans that they can legally buy downloads which are not locked to specific players or computers or mobile phones."

Coultart spoke also on plans to take the campaign international. "We are in discussions with music retail organizations around the world to make 'MP3 compatible' an international standard," he said.

The campaign has the support of Thomson, who licence the MP3 format on behalf of MP3 inventor, the Fraunhofer Institute in Germany.

"We welcome ERA's initiative, which further illustrates the industry-wide adoption of mp3 as the global standard in digital music for its quality, convenience and ubiquity,” said Francois Thuiliere, director of marketing and business development for Thomson's mp3 and Audio Licensing Group in a statement.

U.K. record companies trade association the BPI has also backed the campaign. "Digital music is fast-moving and exciting, so initiatives that help consumer understanding are important," said BPI chief executive Geoff Taylor in a statement. "This logo will not only help give consumers confidence that the music files they are buying will play on a wide range of devices, but will also help them know that they are legal and that artists are getting paid."

ERA is now looking to manufacturers of MP3-compatible digital music players to support the campaign.

Figures from the Official U.K. Charts Company show that last month, single track downloads were up 41% on sales from October 2007 and album downloads had increased by 69% in the same period.