Government scientist Rick Hall on the radiowaves research

The Daily Mail carried a front page splash on a study carried out by military scientists at the Defence Evaluation and Research Agency which suggested that mobile phone signals disrupt part of the brain which controls memory and learning.

Recent studies have already found mobiles - used by nine million people across Britain - can cause a rise in blood pressure and may harm pregnant women.

And they have been linked with brain tumours, cancer, headaches and tiredness.

'No health warning'

But a DERA spokesman, although admitting that the research had taken place, said it was not specifically into the impact of mobile phone signals.

He said: "No health warning has been announced, and the research has been hyped.

"The radio waves tested are those that are used by mobile phones, and it is quite exciting because obviously there is an effect, but we do not know whether it is long term or short term. More research is needed."

Research on rats

Research was carried out on rats

DERA scientists carried out experiments on rats with money from the Defence Ministry and Department of Health.

The research was based on stimulating a slice of rat brain with broadcast radio signals at levels lower than current mobile phone safety limits.

The spokesman said: "It was noted that there was an effect on brain activity. When the radio waves were turned on brain activity stopped or slowed down, and when they were truned off brain activity started again."

A big leap

Dr Alan Preece, a consultant clinical scientist carrying out research into the impact of mobile phone signals on human volunteers, said it was too early for alarm.

Dr Preece said radio waves did penetrate the human head, but most were absorbed in the skin and skull before reaching the brain.

He said: "This research is carried out on rat brain slices, and it is an awfully big step to equate it to the impact on human brains. The public should wait for the outcome of human studies before getting too worried about it."

Dr Preece found radio waves do have impact on short term memory in a previous study, but at much lower frequencies than those used by mobile phones.

Liz Francis, a spokeswoman for the National Radiological Protection Board, said further research was needed on the impact on humans, and warned against generalising from animal research.

She said: "There is nothing at present to suggest any need to change our current line that it is safe to use the current generation of mobile phones."

Some campaigners, however, believe mobile phones should carry warning labels.