The World Health Organisation (WHO) has found links between the use of mobile phones and the development of brain cancer.
The WHO has carried out a 10-year study that has evidence that heavy mobile users have a higher risk of developing brain tumours later in life
The results of the £20m study are expected to be published.
Elisabeth Cardis, who heads the report team, said, "In the absence of definitive results and in the light of a number of studies which, though limited, suggest a possible effect of radio frequency radiation, precautions are important."
She said there should be restricted use by children and methods of reducing exposure such as hands free kits are interesting.