Vendors and pressure groups last week intensified their efforts to crack down on spam, which continues to plague corporate email systems.

However, experts said that the situation is unlikely to improve without the strengthening of national laws and the introduction of tough, globally-agreed legislation.

According to Microsoft, spam now accounts for more than half of all email traffic and cost European companies more than £1.7bn in lost productivity in 2002.

Economic co-operation body the OECD last week launched a new initiative encouraging its 30 member states, including the UK, Japan and the US, to collaborate on action against spammers.

It urged countries to improve international co-operation between consumer watchdogs and to work with industry to garner input and support.

Microsoft, meanwhile, stepped up its battle against spam by suing 15 of the most prolific spammers in the UK and US.

In the UK, the Department of Trade and Industry concluded consultations on implementing the European Commission's Privacy and Electronic Communications Directive, which comes into force on 31 October.

Under the directive UK businesses will have to get customers to opt in to receive marketing emails, rather than to opt out of receiving them.

However, employers' body the Confederation of British Industry maintained that this would present problems for companies.

A spokesman said: "We are concerned that the opt-in requirement goes too far. Email has a role to play in companies promoting themselves."

Commenting on the directive, Malcolm Hutty of Linx, a non-profit consortium of ISPs, stated: "It is important that the information commissioner is funded to make full use of these new powers."

Mike Pullen, of law firm DLA, added that a lot of legitimate firms would respect the opt-in rule, but to stop other spammers the penalties would have to be severe.

"The Information Commission currently only has the power to issue a stop notice. It needs to be able to get firms to wipe their databases," he said.

"As for illegal spammers, the only way to stop them is with massive fines and the threat of jail."

Also in the UK, the All Party Parliamentary Internet Group is running a public inquiry on spam with a view to creating global laws, although such legislation is not likely for at least another three years.