Steve Jobs, Apple's chief executive, published an open letter on Tuesday arguing that selling music online without copyright protections - known as digital rights management - would make it easier for consumers to listen to music on different devices, boosting the overall market.

However, several music executives yesterday dismissed his suggestion as disingenuous and reiterated their argument that inter-operability between devices would be improved if Apple were to license its own DRM to other companies rather than doing away with the protections altogether. They also suggested that Mr Jobs's true motive was to defuse legal problems in Europe, where Apple is being asked to make iTunes compatible with other devices.

Torgeir Waterhouse, senior adviser to Norway's Consumer Council, said Mr Jobs was "pushing the ball as far away from himself as he can".

While all the major record companies have experimented with releasing songs in MP3 format, which contains no DRM, only EMI currently appears likely to embrace such a format more widely.

Last week, EMI launched the first single from Norah Jones's new album as an MP3.

However, Gene Munster, analyst at Piper Jaffray, said: "My bet is, at the end of the day, the record labels want some form of DRM."

Music companies have long complained that Apple has reaped the majority of the benefit of online music through sales of its iPod device, while the music that fuels it is either traded illegally or under-priced.

Last year, Mr Jobs rebuffed their request to introduce variable pricing on iTunes in place of Apple's 99 cents per track model.

However, several record executives said yesterday they would take a tougher line on variable pricing when their iTunes contracts come up for renewal from this May, and may also push for some share of iPod revenues.