Attempts to combat spam, the scourge of email users the world over, would be hampered if the US fails to introduce an outright ban, according to a senior European Commission official.

A law banning unsolicited emails comes into force in the 15-member states this Autumn. The law prohibits email marketers in the Union from sending their promotions to individuals unless those targeted have expressly asked to receive promotions.

The US government appears to favour an opt-out approach, whereby marketers can flog their wares to anyone by email unless the person targeted asks to be removed from the target list.

Yesterday's initiative by the Commission, described as its "second step" in the spam war, seeks to promote international co-operation and to raise public awareness of how individuals can help in tracking elusive spammers down.

"There is a growing awareness that you cannot tackle spam alone," says Erkki Liikanen, commissioner for enterprise and the information society. "We need to work with international partners."

But co-operation with the US "would be restricted if we end up with an opt-out system in the United States," says Philippe Gerard, an official in Liikanen's department.

"The US authorities appear to be focusing only on spam that is deceptive or worse. We, on the other hand, believe that even the harmless spam messages are a serious problem because of the enormous volume of them," Gerard states.

The Commission estimates that the loss in productivity due to spam cost EU businesses around ?2.4bn (£1.7bn) in 2002. Lost productivity includes the value of the time wasted clearing out messages from peoples' inboxes and the loss of performance from PCs clogged up with unsolicited emails.

"If there was any co-operation with the US, it would only be in areas where we both agree action is needed," says Gerard. "The deluge of harmless but annoying spam messages would therefore not become a common enemy, " he adds.

Liikanen refrains from criticising the US' approach to combating spam: "The US is seriously working on the issue. The [US] Federal Trade Commission is looking for a solution," he says. But he adds that he remains "sceptical" about an opt-out approach. "It will always be less efficient than an opt-in rule," Liikanen says.

Stefano Rodota, president of the Italian Data Protection Commission, says that even if the US does choose the opt-out route, American businesses will go further to stamp out unsolicited emails.

"A big part of the business community in the US is moving towards opt-in because firms such as [consumer goods giant] Procter & Gamble view spam as a threat to their abilities to sell their products over the net," Rodota says.

Europe's internet service providers welcomes the Commission's latest efforts to fight spam. "The new rules on spam are a crucial tool in the ongoing battle of ISPs to limit the damage caused by this incessant and ever-changing problem, both to themselves and to their customers," trade association EuroISPA says in a statement today.