Companies sending email or text message adverts will have to get the permission of recipients first, under rules published yesterday by the advertising standards authority.
The growth in new media has been accompanied by a steep rise in junk mail on the internet and unwanted messages to mobile phones. The ASA has seen a six-fold rise in the number of complaints about direct marketing text messages in the past year.
The new code of practice is an attempt to catch up with the technology and control some of the abuses. It says explicit consent must now be given for marketing by email or text message.
Unsolicited email advertising (spam) must now also be clearly marked so recipients can see what it is before they open it.
More than 76% of home email users receive spam every day, according to research conducted by Brightmail, a company that filters out 3bn unwanted emails a month for BT Openworld customers.
BT Openworld welcomed the code but said no one organisation could solve the problem. "It can be quite difficult to control legally because emails are coming from all over the world," a spokesman, Tony Henderson, said.
Most spammers obtain email addresses after people sign up for goods or newsletters on websites. But the technology also exists for companies to generate random addresses until some work. Computers generating random mobile numbers are also the source of many unsolicited text message adverts, although people signing up to services online frequently find their numbers passed on.
Companies sending the messages often trick users into phoning premium rate numbers. Sending romantic messages from anonymous admirers is a favourite method. One complaint was about a text message advertisement that urged the recipient to report to an army recruitment centre.
The code also covers online banner ads and pop-up ads on the internet.
Andrew Brown, who is chairman of the ASA's committee of advertising practice, said: "Effective self-regulation is paramount to consumer confidence in marketing. We have to ensure that marketers have clear guidelines on how to keep their marketing communications legal, decent, honest and truthful."
