Over a third of UK firms are flouting EU regulations on email privacy, according to a report by data management firm CDMS.
The guidelines are designed to ensure that recipients have had the opportunity to opt-in to promotional emails.
Under the European Directive on Privacy and Electronic Communication it became mandatory to offer opt-in in December 2003.
The Information Commissioners Office (ICO), which monitors such activity, explained that it can be difficult to clamp down on the offenders most of which appear to be based overseas.
Critics of the ICO insist that it does not have the teeth to deal with the problem and that, although it has the power to impose fines up to £5,000, it has yet to do so.
The ICO said that it receives 10,000 complaints a year but that the majority relate to nuisance phone calls.
Part of the problem of unsolicited email is that marketers in the US have only to provide an opt-out option, something that is strongly criticised by privacy groups.
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