Parents should ensure their children use mobile phones only when necessary because of the potential health risks, a leading expert is warning.

The latest study by Sir William Stewart will remind people while there is still no proof mobile phones are unsafe, precautionary steps should be taken.

Five years ago, he said children should only use mobiles in emergencies.

But Sir William, of the National Radiological Protection Board, is now concerned that advice is being ignored.

One in four seven to 10-year-olds now own a mobile phone - double the levels in 2001, according to latest figures.

Sir William's report, to be published in full later on Tuesday, will warn that if mobile phones do damage health, then children will inevitably be at greatest risk.

It will also call for a review of the planning process for base stations.

Sir William told the BBC Radio Four Today programme there was no absolute evidence that mobile phones were a risk to health - but various studies had raised serious concerns.

It would be wrong to allow children under eight years old to use mobile phones regularly, he said.

He said: "If there are risks - and we think that maybe there are - then the people who are going to be most effected are children, and the younger the children, the greater the danger.

"Parents have a responsibility to their children not simply to throw a mobile phone to a young child, and say 'off you go'."

Professor Lawrie Challis, who was vice chairman of the Stewart Inquiry and is now chairman of the Mobile Telecommunications and Health Research programme, set up to investigate the health risks of mobile phones, told BBC News: "I would certainly not wish my own grandchildren to use mobile phones more than they had to."

Since the UK government-commissioned Stewart report concluded there was no evidence of harm associated with using mobile phones but recommended a precautionary approach for children, experts have remained divided over whether the phones pose a risk.

'Harmful'
Last year a 750-people study by Sweden's Karolinska Institute suggested using a mobile phone for 10 years or more increases the risk of ear tumours by four times.

A Dutch study has suggested mobile phone use can affect brain function, and further research from Europe indicated radiation from the phones can cause DNA damage.

But Dr Andrew Burgess, a lecturer in sociology at Kent University, published research a year ago dismissing claims mobile phones were harmful.

He said: "I do not know why these latest warnings are being made, they are exactly the same as was said five years ago.

"As far as I am concerned mobile phones are safe to use.

"There may be some unknown risk that could appear at some unknown date in the future but we have to balance that against the benefits of using them."

And Mike Dolan, executive director of the Mobile Operators Association, said there were good reasons why children carried mobile phones.

"Families do go out there and purchase mobile phones for their children very often for very tangible security benefits."

From BBC News