Online retail giant Amazon has warned a US court that Google will stifle competition and break anti-trust laws if it is permitted to add millions of book titles to its digital library.

Amazon told US District Court Judge Denny Chin that Google’s proposed settlement with authors and publishers was a “high-tech form of back-room agreements that are the stuff of anti-trust nightmares”, according to The Telegraph.

Google would be able to digitalise books in which the copyright holder could not be found. Amazon said it always gets copyright permission from the copyright holder before it scans books for its own digital service, Kindle.

Amazon said Google’s approach would fundamentally change copyright law, and has joined forces with Microsoft, Yahoo! and literary organisations to form the Open Book Alliance. It is opposing Google’s proposed settlement that would see the online search giant pay $125m to create a Books Rights Registry that would allow authors and publishers to register titles and receive compensation.

Authors have until today to tell Google if they do not want their books digitised.

Susan Benton, president of the Urban Library Council, said: This is a pivotal moment in the history of access to recorded information, not unlike the introduction of moveable type or the birth of the internet.”

A Google spokesperson said: “The Google books settlement is injecting more competition into the digital books pace, so it’s understandable why our competitors might fight hard to prevent more competition.”