More than half of all emails sent to individuals and businesses by September 2003 will be spam, and a fifth of these unsolicited mails in the UK will be pornographic, an industry vendor claimed yesterday.

According to monitoring by spam filtering firm Brightmail, during the past five years spam attacks have rocketed from a few hundred a month to nearly 7.5 million in May 2003.

The company said that, in April 2001, seven per cent of the email it checked was spam. As of June 2003, it found that over 48 per cent of all email traffic on the internet is unsolicited.

Brightmail said that its monitoring has also found that spam email in the UK is rapidly becoming more offensive.

In June 2003 over 20 per cent of spam was pornographic, making it the second largest UK spam category following the 34 per cent of spam offering products for sale.

In the US only 19 per cent of spam fell into the adult category in June.

Speaking at the UK Spam Summit, Enrique Salem, chief executive at Brightmail, said: "No one thought that spam would be the primary use of email, so they did not have solutions built in to provide better security.

"The spam we saw six months ago is not the spam that we see today. We are in an arms race."

Salem believes that the spam problem could be "under control in the next three years", provided that there are combined efforts from ISPs, technology companies, legitimate direct marketing firms and legislation.

While the volume of adult spam is disturbing, the largest category of spam continues to come from illegitimate direct mail companies that offer products to email users who have not requested to be contacted.

Stephen Timms, minister for energy, e-commerce and postal services, said that the government recognised that spam is a growing problem, and one that could put people off using the internet.

"This is an area where there are huge problems and great frustrations. But it is an area where there are solutions as well," he said.

"We don't want to suggest that spam will disappear, but well thought through regulation, industry action and user awareness can help make big inroads."

Additional reporting by Rob Jones.