The International Agency for Research on Cancer, part of the World Health Organisation, has classified the radiation emitted by handsets as “possibly carcinogenic” although it did not find evidence of a clear link.

Its decision - putting mobiles in the same risk category as lead, the pesticide DDT and petrol exhausts - will put governments under pressure to update their advice to the public on the potential dangers of talking on mobiles for long periods of time.

Christopher Wild, the director of IARC, said that while more research is carried out “it is important to take pragmatic measures to reduce exposure such as hands-free devices or texting”.

It has long been known that the radiofrequency electromagnetic fields emitted by mobile phones are absorbed by the body, much of it by the head when the handset is held to the ear.

But research into the possible health consequences of frequent mobile use has proved inconclusive because the technology has only been widely used for a few years while it can take decades for tumours to develop.

Last year a landmark IARC study, known as Interphone, disclosed that making calls for more than half an hour a day over 10 years could increase users’ risk of developing gliomas - a type of tumor that starts in the brain or spine - by 40 per cent.