Sir William Stewart, chairman of the Health Protection Agency, is expected to say this week that new evidence of potential health problems reinforces the need for children to use the phones only for essential calls.

He issued similar advice five years ago and is known to be concerned that it has been largely ignored. The proportion of children with phones has doubled since then as companies have promoted their use to the young. Stewart, who has barred his own grandchildren from using the technology, accepts that although there is no proof that mobile phones damage health, children need to limit their use as a precaution.

His scientists believe that if there are as yet unknown risks from mobiles, children may be more vulnerable because of their developing nervous systems, the greater absorption of energy into the tissues of the head and a longer lifetime of exposure.

Stewart, chairman of the National Radiological Protection Board (NRPB), was appointed by the government to monitor mobile phone safety. His guidance, to be published on Tuesday, is expected to call on mobile telecoms companies to stop targeting children.

Among the most controversial moves have been attempts to encourage their use among children at primary schools. The British firm Communic8 recently launched MyMo, a phone aimed at children aged from four to eight.

According to a report by Mobile Youth, a mobile telecoms consultancy, a quarter of primary school children now own a mobile. The figure rises to 90% among 11 to 16-year-olds, according to research by Sheffield Hallam University.

The industry has directly challenged the NRPB’s advice that children should limit their use of mobiles. The Motorola website states: “There is no scientific basis to restrict the use of mobile phones by children and this remains a matter open for parental choice.”

The Stewart report is, however, expected to advise children and adults to take a “more precautionary approach”.

It will question whether mobile phone use is in danger of getting “out of control” and say that, though the weight of evidence does not show that mobile phones are dangerous, they have only been in use for a relatively short time and the possibility of health risks remains.

Of particular concern to the NRPB is a report published by researchers at Sweden’s Karolinska Institute in October, which showed that people who had used mobile phones for 10 years or more had an increased risk of developing acoustic neuroma, a benign tumour regarded as serious because of its position next to brain tissue.

In December, EU-backed research found that mobile phones can potentially cause cancer. The £2.2m Reflex study did not prove that mobile phones represent a serious health risk but provided worrying results in laboratory tests.

Human tissue was exposed to mobile phone radiation and the results showed that the radiation was able to damage DNA in human cells.

A spokeswoman for the Mobile Operators Association, which represents the five UK network operators, said: “It is up to parents whether they give their children phones. They must weigh up the possibility of future unknown health risks with the security benefits to children of carrying a mobile.”

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