A BBC Panorama investigation, to be broadcast tonight, has discovered Wi-Fi networks in schools can give off three times the height of the signal radiation of phone masts.

The Chairman of the Health Protection Agency, Sir William Stewart, calls for a review of the health effects of Wi-Fi in the programme, to be broadcast tonight on BBC One.

Current Government advice – from a report published by Sir William in 2000 – recommends that phone masts are not sited near schools because children are thought to be more vulnerable to radio frequency radiation emissions than adults.

Panorama visited a comprehensive school in Norwich and measured the radiation signal strength from a classroom Wi-Fi-enabled laptop.

The programme found the height of the signal strength was three-times higher than the height of the signal strength of a typical phone mast.

Children's skulls are still growing and are thinner than adults' – tests have shown children absorb more radiation than adults when using mobile phones – which could raise questions about the safety of children working bent over computers being exposed to radiation at very close-quarters.

The school Panorama visited had nine classrooms with Wi-Fi nodes in operation, with plans for more. Seventy per cent of secondary schools in the UK already have Wi-Fi and nearly 50% of all primary schools do.

Panorama spoke to nearly 50 of those schools and only one had been alerted that there might be possible health risks. Some others had been told that there was no risk.

The full programme "Panorama: Wi-Fi – A Warning Signal" is due to be broadcast tonight at 8.30pm on BBC One.