“We found no association between incidence and exposure for people who have used their phones for less than 10 years,” said Lawrie Challis, chair of the Mobile Telecommunications and Health Research programme.

“But we cannot rule out the possibility (of) an association for exposures for more than 10 years. The numbers appeared to show some slight hint... it needs to be followed up.” The £8.8m MTHR programme is a joint project funded by government and the mobile phone industry in response to Sir William Stewart’s independent inquiry in 2000 into the safety of mobiles. He has concluded that mobile phones seem to pose no problems but has recommended further research.

The group’s report, published on Wednesday, collates the work of 28 studies it has backed, as well as other research from around the world. It concludes that there is no evidence of short-term effects from either GSM or 3G handsets or base stations.

For the long term, however, there is less certainty. Paul Elliott, an epidemiologist at Imperial College London, said: “In some of the studies, there was an excess of malignant brain tumours. But the excess is quite small and is at the borderline .”

Regarding the effects on children, Professor Challis said: “At this stage we have no evidence at all that mobile phones hurt children”.