Spam has become so bad in the US that even advertisers have admitted that restrictions are needed.

The Direct Marketing Association (DMA), which once opposed any federal anti-spam legislation, says it will now lobby for federal and state laws to control the growth of million-message batches of emails.

A daily flood of spam vexes consumers and internet service providers (ISPs) alike, whose attempts to block it are circumvented by stealthy emailing technology, says the DMA, which has 4,700 members.

Jerry Cerasale, the DMA's vice president for government affairs, told Reuters that the sheer volume would swamp the medium, rendering it useless.

The guidelines proposed by the DMA would prohibit marketers from sending unsolicited emails that use deceptive identifiers, such as false subject lines and return addresses.

Cerasale said marketers should be required to list the physical address and contact information of the business on whose behalf the message is sent. And, he said, a prominent "unsubscribe" option should be available for recipients who wished to halt further mailings.

The DMA supports unsolicited email marketing as long as it targets a certain demographic or interest group - 25 to 35-year-olds or homeowners, for example - and is not merely sent to every email address that can be gathered.

But the Coalition Against Unsolicited Commercial Email (CAUCE) has warned that although the plan "might clear out some of the scam artists" it would probably increase the amount of unsolicited emails sent by legitimate companies.

A CAUCE spokesman said that email marketing should only be done at the recipient's request - or from companies with which the recipient is a customer.

Tom Cowles, who heads Empire Towers, one of the world's largest bulk emailers, has backed the DMA proposal because he believes it will give his business more legitimacy.

He said spammers have been forced to cloak their messages with fake headers and use other deceptive identifiers because anti-spam activists harangue the ISPs who host their businesses.

When the service provider discovers the spam business, the spammer's website is often taken down - and with it disappears the software to remove the recipient from future unsolicited mailings.

Cowles said guidelines should restrict email content while forcing ISPs to host marketers that follow the rules.