New rules to tackle spam email and other forms of intrusive marketing come in to force in the UK today.

The rules will give phone, fax and Internet users more control over how their personal details are used, meaning that companies will not be able to send unsolicited emails or text messages to consumers, unless the recipient has agreed in advance to receive them.

Business-to-business e-marketing is not affected by the new legislation, but all direct marketing email must now include proper sender and contact details, and an opt-out clause.

In addition, companies that use tracking devices (cookies) on their Web sites will now have to tell users they are doing so and provide an opportunity to reject them.

Communications Minister Stephen Timms said: "Breach of enforcement orders issued by the Information Commissioner is a criminal offence liable to a fine of up to £5,000 in a magistrate's court, or an unlimited fine if the trial is before jury.

"Anyone who has suffered damages because the regulations have been breached has the right to sue the person responsible for compensation".

The law is based on an EC Directive on Privacy and Electronic Communications that obliges member states to introduce their own anti-spam laws. The deadline for the introduction of these laws was October – only the UK and five other EU countries have implemented regulations.

But new research from WebAbacus suggests many UK Web sites are already breaking the new rules. According to the online marketing advisory, 98 per cent of firms do not give enough information about files which track user movements, or provide a simple opt-out option.

WebAbacus's Ian Thomas told the BBC: "Companies are either not aware of the legislation, or are ignoring it."

Assistant information commissioner Phil Jones told the BBC that the information commissioner was "very surprised so many Web sites were not doing what is required, even though these regulations have been on the horizon for a long time". He added: "There should be transparency. People should know what is going on with the information collected about them."

Founder of anti-spam organisation The Spamhaus Project Steve Linford doesn't believe the new law will make a difference. He told the Independent: "The problem is that £5,000 is nothing to a spammer - these people are making £20,000 per week."

He told the BBC: "The whole problem with these laws is that they are geared to spammers being honest and respecting laws. Of course there are no honest spammers - the whole profession is based on deceit."

Other critics argue that even when all fifteen EU members introduce anti-spam legislation this will not stem the tide of unsolicited email, much of which originates from the US and beyond.

A government spokesperson told NetImperative that it is now discussing anti-spam legislation with US officials. The spokesperson from the Department of Trade and Industry said: "We realise that spam is a global problem and we are in discussions with the US about how best to tackle spam on a global basis."

Filtering company MessageLabs estimates that last year less than 10 per cent of e-mail worldwide was spam; now it is thought to be half of the total.