Computers with wireless internet should not be placed on children's laps, says the head of the government's committee on mobile phone safety research.
Prof Challis says children should not use wi-fi laptops on their laps
Professor Lawrie Challis told the Daily Telegraph children using wi-fi networks should be monitored until research into potential health risks is completed.
He says children should keep a safe distance from the embedded antennas.
The Health Protection Agency has said wi-fi devices are of very low power - much lower than mobile phones.
Prof Challis, retired professor of physics at the University of Nottingham, said: "With a desktop computer, the transmitter will be in the tower.
"This might be perhaps 20cms from your leg and the exposure would then be around one per cent of that from a mobile phone.
"However, if you put a laptop straight on your lap and are using wi-fi, you could be around two centimetres from the transmitter, and receiving comparable exposure to that from a mobile phone."
Prof Challis added that children are much more sensitive than adults to dangers such as pollutants like lead and UV radiation.
"So if there should be a problem with mobiles, then it may be a bigger problem for children.
"Since we advise that children should be discouraged from using mobile phones, we should also discourage children from placing their laptop on their lap when they are using wi-fi.
Meanwhile, teachers have called for an investigation into whether there are any health risks from wireless computer networks in schools.
The Professional Association of Teachers union is writing to the education secretary for a clarification on wi-fi safety.
Many primary and secondary schools use wi-fi networks - but the PAT believes there is insufficient long-term evidence to demonstrate whether such networks are safe.