SAN FRANCISCO -- A new Internet worm has surfaced that criticizes British Prime Minister Tony Blair and launches an attack attempting to knock a U.K. government website off the Internet, anti-virus software provider Sophos Plc said.

The worm, dubbed "Quaters," spreads via E-mail using a variety of subject lines, such as "Your Account Information," and spreads in Internet chat relay systems posing as an attempt to break an Internet chain mail world record.

It overwrites files on a user's computer and displays a message that accuses Blair of wasting taxpayer money on immigrants instead of spending it on the national health service and schools.

"Think about it Mr. Blair. Your career depends on it, we've had enough," the message says in part, Reuters reported.

Quaters also tries to launch a denial-of-service attack on the website of the prime minister's office, http://www.number-10.gov.uk, Sophos said.

There have been few reports of the worm circulating on the Internet, British-based Sophos said.

The malicious program is not the first to target a British prime minister.

In the 1990s, the Fu Manchu virus replaced the name of former Prime Minister Margaret Thatcher with an expletive whenever it was typed, said Chris Belthoff, a senior security analyst at Sophos.