Microsoft and Yahoo have joined a group of opponents that is against Google's right to digitise millions of books.

The companies have become part of the Open Book Alliance, made up of non-profit organisations and libraries that have raised a red flag against Google's plan to digitise books and put them on the internet.

A spokesperson for Microsoft and Yahoo confirmed to Reuters that they had joined. A spokeswoman for Amazon.com claimed that it didn't “comment on rumour or speculation”, after rumours were made that it too had reportedly joined.

The opposition to Google's book digitising, claim that it allows them to set prices for libraries once they scan books and put them on the internet. Also if the service becomes a necessity for libraries they could face monopoly pricing. It would also allow Google to digitise so-called orphan works - books or other materials that are still covered by US copyright law, but it is not clear who owns the rights to them.

However Gabriel Stricker, a spokesman for Google, denied this, claiming: “The agreement is not exclusive. If approved by the court it will expand access to millions of books in the US. The agreement stands to inject more competition into the digital book space, so it's understandable why our competitors would fight hard to prevent more competition.”

The deal is under review or investigation by the US Justice Department, the European Commission and a group of US state attorneys general.

The proposed settlement was reached in October 2008, to settle a lawsuit filed in 2005 by the Author's Guild, when Google began scanning books. The Guild and a group of publishers had alleged copyright infringement.

Google has agreed to pay $125 million to create a Book Rights Registry, where authors and publishers can register works and receive compensation from institutional subscriptions or book sales. A hearing on approval of the settlement is set for 7th October in the US District Court in New York.