The UK manufacturing sector is being particularly severely hit by the rising global tide of unsolicited spam emails, research has claimed.

According to figures released by managed email firm MessageLabs, more than four out of every five emails received by manufacturing firms over the past year were spam.

But the study found that viruses were the biggest problem among not-for-profit and healthcare organisations, where one in every six emails contained malicious content.

The government and public sector (one in nine), retail (one in 10), education organisations (one in 12) and building and construction companies (one in 14) also suffered from sustained and regular attack.

The sectors best protected from viruses were in professional services, such as legal firms, which received one virus in every 38 emails, and financial services companies which received one virus in every 29 emails.

Government and not-for-profit sectors fared better against spam, with only 19 per cent of government email classified as unsolicited and only 24 per cent in not-for-profit organisations.

Mark Sunner, chief technology officer at MessageLabs, said: "The severity of these attacks is unsurprising, as 2004 marked a sea-change in terms of email security threats to business.

"The convergence of viruses and spam is now dominant; almost all viruses released in 2004 contained some additional component allowing the infected machine to become a spam sending zombie. So it is of little surprise that all sectors of UK Plc were badly hit."

Sunner drew particular attention to the spread of the attacks. "In previous years the companies most affected tended to be those dealing mostly with less-protected home users," he said. "This year there does not appear to be such an obvious trend."