Spam touting anti-spam services is appearing in many inboxes.

Frustrated internet users inundated with unwanted get-rich-quick schemes and herbal Viagra offers may have noticed a new, unsolicited pitch promising to reduce the amount of 'spam' email they receive.

Pointing to websites with names such as remove.org and globalremoval.com, the messages promise - for a nominal fee - to stop spam at its source by placing their addresses on a 'do not spam' registry.

The services say they have hit on a novel and cheap way to reduce spam, and point to bulging customer lists as proof. But government and private sector experts say such 'do not spam' services are not likely to work because marketing firms are under no obligation to comply.

Howard Beales, head of the Federal Trade Commission's consumer protection division, said: "It's probably not worth signing up. You can get plenty of spam for free."

Ironically, many of the do-not-spam services may have been inspired by an FTC initiative in the US - the telephone 'do not call' list that promises to keep most telemarketers at bay, starting in October.

The popularity of the anti-telemarketing list and the success of similar state-level programmes have prompted some to call for a 'do not spam' list.

The FTC and many technology experts say a government-backed 'do not spam' list would do little good, as spammers, unlike telemarketers, often cloak their identities and thus could easily escape punishment. Also, some marketers might view the list as a tempting trove of valid email addresses to sell to other spammers.

While prospects for a US federal 'do not spam' list look doubtful, private companies have stepped in to offer their own services, often through unsolicited messages of their own.

Remove.org promises to rid members' inboxes of spam and protect their children from unwanted pornography for $9.95 per year.

The company seeks to cut off internet marketers who send unsolicited messages to the list's 50,000 members by notifying their internet providers that the spammer may be violating their service contract, remove.org marketing director Charles David said.

Internet marketers who do not wish to generate consumer complaints or send pornography to children can scrub their master lists of members' email addresses, he said - a key consideration as public anti-spam sentiment mounts. "I think they really see their days as potentially numbered, and the current climate's given us that extra leverage," David said.

Another service, globalremoval.org, deputises internet marketers to seek out those who are sick of spam. Consumers pay $5 for a lifetime membership and the marketers get $1 for each internet user they sign up. The list is encrypted to keep it out of spammers' hands, and those who participate sign a contract to be held accountable.

Company founder Tom Jackson said the system had proved its appeal, saying "tens of thousands" had signed up in recent weeks, some in response to globalremoval.org's own email campaign.

"If that message upsets people, then I say 'either sign up with us or pretend it was one more Viagra ad and get back to your spam diet, and we're really sorry to have bothered you,'" Jackson said.

Several industry and technology experts say 'do not spam' lists are unlikely to succeed without a federal law.

Dave Brussin, chief technology officer of the ePrivacy Group, which wants Congress to pass a national list, said: "To the best of my knowledge, these private remove services are nothing but scams."

Computer security consultant Richard M. Smith says working with spammers to cut spam is a conflict of interest. "Doesn't pass my smell test," he said.

Louis Mastria, a spokesman for the Direct Marketing Association, which represents many internet marketers, said: "The whole concept is a little fishy. They have no power over these guys, so there's no real service that they can guarantee or provide.

"You've spent your $10 and what do you get out of it?"