AltaVista, the internet search engine, is the latest company to try to use patent law to claim monopoly rights over a fundamental online technique. The company has claimed that it owns a patent on a method of indexing websites which is used by most search engines and company intranets.

"We believe that virtually everyone out there who indexes the web is in violation of at least several of [AltaVista's] key patents," said David Wetherell, the chief executive of CMGI, AltaVista's parent company, in a recent interview with the US magazine Internet World.

He said the company would pursue the issue this year, using lawsuits "if necessary" to force companies it claims are infringing its patents to pay copyright. AltaVista owns 38 patents, "many of which we think are fundamental in the search area", and the company has applied for a further 30, Mr Wetherell said. "If you index a distributed set of databases - that's what the internet is. And even within intranets, that's one of the patents."

The financial incentive for the threatened litigation is clear: the downturn in the online advertising market is taking its toll, and AltaVista in January laid off 25 per cent of its staff. Mr Wetherell insisted the company was "doing well in the advertising space", but said it needed to "leverage its position in search licensing to a greater extent. And we saw the opportunity to do that because we think it's a big market."

But until the debate over software patents is resolved in Europe, it is unlikely that law courts would enforce patents such as AltaVista's.

Email Jean Eaglesham at jean.eaglesham@ft.com