Up to 1 million Telewest broadband customers have had their computers blacklisted by an anti-spam register that says the company is failing to act against spammers who use sophisticated "zombie" programmes to take over their clients' PCs.

The Spam Prevention Early Warning System - or Spews - whose blacklist is used by many internet service providers to help fight unsolicited e-mails, said it was listing a range of IP addresses because of the high number of Telewest customers whose machines have been compromised by computer worms which allow spammers to control them remotely.

PCs on broadband networks are particularly sought after by spammers for their "zombie armies" since they are online for much longer periods and have higher bandwidth that can be used to send e-mails without the owner's knowledge.

Recent research by web security firm Symantec shows that 25 per cent of the world's remotely controlled PCs are found in Britain - helped by the rapid uptake of broadband and widespread ignorance about web security. The compromised computers are being used to send spam, launch attacks on websites and steal identities.

A Telewest spokesman, John Moorwood, said that the company was doing everything it could to sort out the problem, contacting customers directly and telling them how to clean up their PCs.

He said Telewest had not received any complaints from customers yet about their e-mail systems not working, and only had around 700,000 customers on its Blueyonder broadband service.

Telewest reckons the number of compromised computers on its network numbers in the "low thousands" - and although it is taking the Spews recommendation seriously, it does not agree with it. Newsboard postings suggested that many others agreed that the Spews recommendation was unncessarily heavy-handed since, at most, only 20,000 computers are thought to be infected by the Zombie viruses.

The blacklisting should not, however, affect most Telewest customers, who use Telewest's own mail servers, or web-based services like Hotmail, to send e-mails. But those who have set up their own mail servers on their machines could find themselves blacklisted - along with the spammers.

"There are plenty of legitimate non-Telewest mail servers being run on our network and to block all non-Telewest traffic on our network would prevent customers from using them," Mr Moorwood said.

"So in other words we dont agree with the view from Spews at all. Blocking all non-Telewest IP addresses wouldn't be a forward thinking solution."

Mr Moorwood also denied an accusation on the Spews website that Telewest was a "poorly run broadband network company when it comes to dealing with abuse".

He said: "We have spam and virus filters on our network and monitor our network 24/7.

"To suggest that we're a poorly run broadband outfit is wrong - we strongly dispute that. We are one of the most successful and innovative broadband companies in Britain. In fact we were the first company to launch broadband services in Britain."

The high number of spam e-mails being sent from Telewest addresses was revealed a month ago by Silicon.com, the internet news service. According to Senderbase, which monitors global e-mail traffic, blueyonder.co.uk addresses are generating more than 90 million e-mails a day - the ninth most active in the world. Hotmail customers, with 170 million registered addresses, generate 97 million a day.

Mr Moorwood said Telewest would launch a bundle of free anti-spam, anti-virus and firewall software in the next few months to help customers keep their computers safe. In the meantime, customers were advised to install up-to-date firewall and anti-virus software.

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