Government-appointed experts are calling for an investigation into possible links between radiation from power lines and childhood leukaemia.
Scientists are divided over the risks of living under power lines
The National Radiological Protection Board found those exposed to long-term electromagnetic radiation levels above 0.4 microtesla are at double the risk.
Around one in 200 homes fit this category - but overall risk is small.
But the board, which reviewed research into the issue, stressed no causal link was proved by the findings.
It also concedes that the leukaemia findings may be no more than a statistical quirk.
The board has also brought Britain's safe radiation level in line with international regulations at 100 microteslas over a 24-hour period.
This is down from 1,600 microteslas over 24 hours.
Dr Alastair McKinlay, an NRPB expert, said at this stage further restrictions on levels of exposure were not needed - but he said it would be wrong for ministers to ignore the leukaemia issue.
The Department of Health said it had already opened talks with the NRPB concerning precautionary measures for power lines.
Most households are exposed to electromagnetic radiation levels of between 0.01 and 0.1 microteslas.
Standing directly below a 400 kilovolt power line might expose a person to levels as high as 40 microteslas, but the dose diminishes rapidly as distance from the source increases.
The leukaemia finding calls into question the safety of far lower levels of exposure continuing over long periods of time.
However, the finding only emerges when studies are considered en masse - no single study has produced hard evidence of a link between proximity to power lines and increased childhood leukaemia rates, the board says.
The NRPB's revised guidelines for electromagnetic radiation safety limits affects both power lines and mobile phones.
The guidelines for mobile phones were adopted in the UK in 2000.
Under the new advice they will now cover all the frequency ranges up to 300 gigahertz produced by TV and radio transmissions, mobile telecommunications and the supply and use of electricity.
Power lines are low frequency radiation sources, generating fields in the 50 hertz range.
There is no clear reason why exposure to electromagnetic radiation should cause leukaemia.
One of the largest investigations to focus on power line radiation, the UK Childhood Cancer Study, found no evidence of increased risk.
A Department of Health spokesman said: "The government has recently started discussions with interested organisations to consider power lines and NRPB advice suggests that this process should continue.
"Discussions will look at whether any precautionary measures would be appropriate and what the practical applications of these might be."
However, campaigners say evidence of a possible risk has been available for more than a decade.
'Small step forward'
Chairman of the environmental campaign group, Revolt, Mike O'Carroll said the call for a new investigation was a small step forward.
"The evidence on electro-magnetic fields is much more significant than the evidence the government had against BSE when they accepted it was the most likely cause of new variant CJD," he said.
"There's no case for starting to dismantle all the electricity pylons but there is a case for allowing the health aspects to be considered when looking at planning applications."