Internet users face regular “brownouts” that will freeze their computers as capacity runs out in cyberspace, according to research to be published later this year.

Experts predict that consumer demand, already growing at 60 percent a year, will start to exceed supply as early as 2010 because of more people working online and the soaring popularity of bandwidth-hungry Web sites such as YouTube and services such as the BBC’s iPlayer.

It will initially lead to computers being disrupted and going offline for several minutes at a time. Beginning in 2012, however, PCs and laptops are likely to operate at a much reduced speed, rendering the Internet an “unreliable toy.”

When Sir Tim Berners-Lee, the British scientist, wrote the code that transformed a private computer network into the World Wide Web in 1991, the Internet appeared to be a limitless resource.

However, a report being compiled by Nemertes Research, a respected American think-tank, will warn that the Web has reached a critical point and that even the recession has failed to stave off impending problems.