Napster's plans to transform itself from a renegade song swapping service into a paid-up member of the music industry establishment received a setback yesterday when two of the world's biggest companies in the sector said they would develop a shared website to compete against it.

Vivendi Universal-owned Universal Music and Japan's Sony underlined their determination not to cede ground or revenues to Napster by giving first details of plans to use a joint venture named Duet to buy up licensing rights to half the world's music.

"We often thought an alliance with Napster would be the only possibility but I don't believe it is right to give the advantage to pirates," said Vivendi Universal chairman Jean-Marie Messier.

Mr Messier said he was also to approach other, as yet unnamed parties about joining the Universal-Sony accord. "We hope others will join us," he told French economic daily La Tribune.

The development could be a significant reversal for Napster which, with the backing of Bertelsmann-owned record label BMG, has offered the big record companies $1bn (£693m) over five years for the right to use their music online.

Duet, which operates out of San Francisco, is expected to offer both a subscription service and a pay-per-listen option. It would unite online stars including Sony's Jennifer Lopez, Ricky Martin and George Michael, with Universal's Boyzone and Elton John.

Napster is looking to introduce a monthly subscription fee of its own. Earlier this month it was found guilty of copyright infringement at the end of a year-long legal battle with the industry's biggest firms, including Universal, Sony, EMI and Warner.