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, reports the Daily Telegraph.
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.
Earlier this month a study revealed that studies that suggest mobile phones don't cause cancer could be flawed.
In 2004 a study found that 10 or more years of mobile phone use can dramatically increase the risk of developing a benign tumour on the auditory nerve. The Institute of Environmental Medicine at Karolinska Institute in Stockholm, which carried out the study, found that the risk of developing the tumours, known as acoustic neuromas, almost doubled for persons who started using their mobile phone at least 10 years before diagnosis.