The head of Britain's leading health watchdog today urgently calls for a review of potential health risks linked to wireless internet networks in schools.

Sir William Stewart, the chairman of the Health Protection Agency (HPA), spoke after emissions at a school were found to be three times those from a mobile phone mast.

His demand follows growing calls for research into whether children could be harmed by radiation from wi-fi networks.

Current Government guidelines, based on a report by Sir William, recommend that mobile phone masts should not be sited near schools without consultation with parents and head teachers.

The Stewart report concluded that while there was no current proof of health dangers, some studies suggested possible risks and that precautions should be taken with children because they are more vulnerable to radio frequency radiation emissions than adults.

Researchers working for the BBC's Panorama programme found the maximum signal strength one metre from a wi-fi-enabled laptop in a classroom in Norwich was three times that measured 100 metres away from a mobile phone mast nearby.

Sir William, a scientific adviser to the last three Governments, told the programme: "I believe there is a need for a review of the wi-fi and other areas. I think it is timely for it to be done now."

Speaking about his review of the evidence for health risks linked to mobile phones and masts published in the year 2000, Sir William said: "There may be changes, for example in cognitive function... there were some indications that there may be cancer inductions... there were some molecular biology changes within the cell and these were issues that we had to bear in mind."

Sir William was referring to studies such as the one published in 2004 by Anders Ahlbom, professor of epidemiology at the Karolinska Institute in Stockholm, which suggested people who had used mobiles for 10 years were almost twice as likely to develop an acoustic neuroma, a tumour on a nerve connecting the ear to the brain, compared with shorter-term users.

Approximately half of primary schools and four fifths of secondary schools use wi-fi internet networks and around one in five adults owns a wireless-enabled laptop.

Spokey Wheeler, headmaster of Burlington Danes Academy in west London, a secondary school with 850 pupils, said last night: "We are currently looking into installing a wireless internet network.

"We have not been alerted to any potential health risks, but as a result of the concerns now being raised we will quite clearly be examining the issue more closely. I would wholeheartedly approve of calls for further research."

Panorama spoke to representatives of almost 50 schools with wireless networks and only one said it had been alerted to the health issue.

Philip Parkin, general secretary of the Professional Association of Teachers, said: "I think schools and parents will be very worried about it. I am asking for schools to consider very carefully whether they should be installing wi-fi networks."

Safety standards set by the International Commission on Non-Ionising Radiation Protection (ICNRP), which apply in the UK, state the amount of energy absorbed from an electric field or radio wave cannot exceed two watts per kilogram when averaged over 10 grams of tissue.

The Panorama researchers found the radiation levels in the Norwich classroom were 600 times lower than this guideline.

Vivienne Baron, of the campaign group Mast Sanity, said: "Many people have already fallen sick as a result of exposure to this microwave technology.

"Parents have not given consent for their children to be guinea pigs."

However, Prof Malcolm Sperrin, director of medical physics and clinical engineering at the Royal Berkshire Hospital, said: "Wi-fi is a technique using very low intensity radio waves.

"Some people suspect a non-thermal interaction but there is no evidence to suggest that this exists and indeed it is unlikely.

"Radio waves and other non-ionising radiations have been part of our lives for a century or more and if such effects were occurring then damage or other untoward effects would have been recorded and studied."

The Panorama programme Wi-fi: A Warning Signal will be broadcast tonight on BBC1 at 8.30pm.