Microsoft's digital library plans are separate to Google's

The books, which are out of copyright, will be digitised from 2006 and put online as part of Microsoft's book search service next year.

Microsoft is already working with the Open Content Alliance (OCA), set up by the Internet Archive, to put an initial 150,000 works online.

A separate global digital library plan by Google is also under way.

The search giant is spending $200m (£110m) to create a digital archive of millions of books from four top US libraries. It is also digitising out-of-copyright books from the UK's Oxford University.

The Microsoft deal means that 25 million pages from the British Library's collections will be put online and made searchable for anyone. More works will be scanned in the future.

"This is great news for research and scholarship and will give unparalleled access to our vast collections to people all over the world: they will be available to anyone, anywhere and at anytime," said British Library chief executive Lynne Brindley.

Teething problems

Both the OCA, which is also backed by Yahoo, and Google want to digitise the world's books and other works to make them searchable and accessible to anyone online.

But Google's plans have come under fire from the Association of American Publishers and the Authors Guild which have both filed legal action for copyright infringement.

Google has restarted its digital library plans

Google halted its plans because of the action, but said it was restarting them this week.

Google and the OCA are initially concentrating on digitising books and works that are out of copyright and in the public domain in order to quell any further copyright fears.

But Google said it still planned to scan newer books that are in print and under copyright protection at a later stage.

Microsoft has been working with the British Library already, giving infrastructure tools and advice for its National Digital Library plan, which was launched in June.