The US has moved closer to introducing a law to curb spam with the law-makers approving a bill to outlaw most unsolicited e-mails.
Critics say the bill would lead to more spam messages
The House of Representatives has backed a bill aimed at stopping spam by imposing fines and prison sentences.
Spam is a nuisance for many, accounting for about half of all e-mails
Critics of the bill say it could lead to more spam as it would allow businesses to send unsolicited e-mail until they are asked to stop.
US law-makers have tried to come up with anti-spam measures for the past six years. During that time, the amount of unsolicited e-mail has grown to a plague that is undermining the net's most popular means of communication.
The Can-Spam Act of 2003 was passed by a vote of 392-5 early Saturday, following an all-night session of the House of Representatives.
Before the measure becomes law, it must be approved by the Senate and President Bush. But both are expected to support the bill.
The legislation would allow Americans to opt out of receiving unsolicited messages. It effectively treats junk e-mail like junk postal mail, with unsolicited e-mails allowed until the recipient chooses to unsubscribe.
It would override state laws, such as the one in California which says that businesses must get permission before sending a commercial message.
The Can-Spam measure proposes fines and jail sentences for people sending spam. It would also outlaw spammers' attempts to cover their tracks by requiring marketers to identify themselves clearly and avoid misleading subject lines or return addresses.
Pornographic messages would have to be clearly labelled as such to allow users to more easily filter them out.
The bill also authorises the Federal Trade Commission to set up a "Do Not Spam" list of people who do not want any e-mail at all, similar to the commission's popular "Do Not Call" list.
Anti-spam activists say the measure, which is designed to curb the spread of spam, will have the opposite effect.
"With the passage of Can-Spam, spamming will be officially legal throughout the United States," said the anti-spam group Spamhaus in a statement.
"Can-Spam says that 23 million US businesses can all begin spamming all US e-mail addresses as long as they give users a way to opt-out, which users can do by following the instructions of each spammer.
"Anyone with any sense would of course realise that if Can-Spam becomes law, opting out of spammers lists will very likely become the main daytime activity for most US e-mail users in 2004."
The bill is expected to pass the Senate in the coming week and be signed into law by President Bush on 1 January.