Conflicting research on hands-free mobile phone ear-pieces has led to a war of words between the British Consumers' Association and the British Department of Trade and Industry (DTI).

Earlier this year, the Consumers' Association magazine Which? published a study that found mobile phone kits acted as an aerial and channelled three times more radiation to the head than a handheld mobile phone.

Last week's Trade and Industry study says there is "clear and unambiguous" evidence that hands-free phones pose less risk than the normal use of such phones. The consumers' group says the DTI's research method was faulty.

A case in the United States brings into question the health implications of mobile radiation. Dr Chris Newman is suing manufacturer Motorola, claiming his brain tumor was caused by daily mobile phone use.