Beatles record label EMI is suing U.S. music website BlueBeat.com, which it said was offering unauthorized downloads of the Fab Four's tracks for sale.
EMI has not authorized content to be sold on BlueBeat.com, a spokeswoman said.
EMI confirmed it had filed a copyright infringement suit against BlueBeat.com in a U.S. court earlier this week.
BlueBeat.com offers songs for 25 U.S. cents each, around one quarter of what a song would typically cost on the dominant online music retail site iTunes, owned by Apple Inc.
On offer is an extensive list of Beatles albums, both original and recently remastered versions, despite the fact that the band has yet to agree with music providers to the release of its cherished catalog online.
A year ago, former Beatle Paul McCartney said the band was keen to make its music available on Apple's iTunes music store, but that negotiations had stalled.
The settlement of a trademark dispute between Apple and The Beatles' company Apple Corps Ltd had raised hopes among fans and record company executives that the way was finally clear for the catalog to make it online.
McCartney said the dispute holding back online sales of Beatles music now lay between the band and EMI.
He said EMI wanted something we're not prepared to give 'em.
Music industry sources said they suspected EMI's action against BlueBeat could be followed by other major labels whose content features on the site.