London: Mobile phones could be a "health time bomb", say experts who are urging UK ministers to warn the public.

More than 200 academic studies link use of the devices with serious health conditions such as brain tumours, according to a group of leading scientists.

In a report published on Tuesday, they say the UK government is playing down the potentially "enormous" health risks — especially for children, whose smaller, thinner skulls are more susceptible to radiation.

Although the experts concede the links are not proven, they argue that "schools, phone shops and the health care system" should be enlisted into a campaign to reduce mobile phone use.

Their report states: "Both the government and phone companies could very easily do far more to alert the public, particularly children, to the emerging risks and safety measures." It accuses officials of "downplaying uncertainty" over safety.

However, critics stress scientists have found inconclusive evidence and a campaign would cause panic. The authors point to several studies linking long-term mobile phone use to development of a rare brain tumour called a glioma.

A 2008 Swedish study suggested children who use mobile phones are five times more likely to develop it. Other peer-reviewed studies have found inconclusive links to low sperm counts, behavioural problems in children whose mothers used them during pregnancy, and damage to brain cells.

One author, consultant neurosurgeon Kevin O'Neill of London's Charing Cross Hospital, said the latency period for brain tumours is 30 years so it is possible the consequences of phone use are not yet apparent.

The report, Mobile Phone Health Risks: The Case for Action to Protect Children, was released by the charity Mobilewise, set up last year.

It says the UK is lagging behind countries such as France, where phones are banned in primary schools, and Canada, where phone shops offer safety leaflets.

Last month a Danish study of 358,000 people concluded there was no link with brain cancer.