Hands-free mobile phone calls could more than triple the brain's exposure to radiation compared to conventional mobile phone calls, according to a report by British consumer research magazine Which?

The report says the level of radiation depends partly on the distance between the earpiece and the cellphone antenna, and it urges the British government to press for a new European standard for hands-free kits.

The group's initial report in April on the potential dangers of hands-free kits - which were believed to help protect consumers who risk warming their brains by holding mobile phones close to their heads - was dismissed by the government after conflicting research three months ago.