Files without copy protection, they argue, can be freely shared or traded over peer-to-peer networks.

Locked in

The record industry says that file sharing is a key factor in the decline in record sales in recent years.

Most major labels insist on some form of DRM on music offered through download services.

DRM systems can include special formats for media files or proprietary media players.

For instance, people buying tracks from the iTunes store cannot move tracks on to non-Apple portable music devices. Others restrict the number of times a user can copy a file.

Yahoo does not agree.

On the official Yahoo music blog, director of product management Ian Rogers wrote: "As you know, we've been publicly trying to convince record labels that they should be selling MP3s for a while now.

"Our position is simple: DRM doesn't add any value for the artist, label (who are selling DRM-free music every day - the Compact Disc), or consumer, the only people it adds value to are the technology companies who are interested in locking consumers to a particular technology platform."

Dave Goldberg, the vice president and general manager of Yahoo Music urged record labels reconsider their stance on DRM technology earlier this year.

Other companies, such as Wippit and eMusic, already offer MP3 files that can be freely shared.

However much of the music is from independent labels.

'Leap forward'

The release of the Jessica Simpson track from Sony BMG represents the first tentative steps by a major label to release a track without copy protection.

It marks a reversal for Sony BMG who were criticised last year when they released their XCP anti-piracy software on music CDs.

This system used virus-like techniques to hide itself and stop CDs being copied. The row over the software ended up in the US courts.

The new track, costing $1.99 (£1.07), can be personalised before the song is downloaded, allowing users to have their name inserted in the lyrics.

Suw Charman, executive director of the digital advocacy body the Open Rights Group says the experiment is "clearly a gimmick" but still a significant move.

"It's an important experiment," she said. "I hope it's the beginning of a significant movement from them [Yahoo]."

"It sends a strong message about not having to have DRM on everything."

People who responded to the announcement on the Yahoo blog agreed.

"This is a huge leap forward for the music industry. I can't think of one consumer who is OK with DRM," wrote one respondent.

"I'm not into Jessica Simpson or the personalisation idea, but I'm very into the non-DRM idea," said another.

Yahoo have not confirmed whether they will release more unprotected music tracks.