Children under the age of 9 should not use cell phones because of potential health risks, the English Government’s leading adviser on radiation said Tuesday.

The chairman of the Health Protection Agency and the National Radiation Protection Board, Sir William Stewart, said that scientists were still unable to say whether mobiles were safe and advised parents to take precautionary measures. He said that if children aged 9 to 14 must own cell phones they should make only short, essential calls and should have low emission models.

“When it comes to suggesting that mobile phones should be available to 3-to 8-year-olds, I can’t believe for a moment that can be justified,” Mr. Stewart said. “It seems to me ludicrous.

If you have a 9- to 14-year-old and you feel they can benefit in terms of security, then that is a personal judgment parents have to make.”

He called for a review of the planning process for mobile transmission towers and said that recent research made him more concerned about possible health hazards than he was five years ago.

Mr. Stewart, who has advised his grandsons, aged 6 and 8, not to own cell phones, said: “My advice is that they should not have them because children’s skulls are not fully thickened, their nervous systems are not fully developed, and the radiation penetrates further into their brains.

“They are also going to use mobile phones for a longer period of their lives and it takes a long time for effects to come through. We are recommending a precautionary approach. There is still no hard evidence that the health of the public has been adversely affected by the use of mobile-phone technology.

“However, we cannot put our hands on our hearts and say that mobile phones are safe.”

There are about 52 million cell-phone users in England. The proportion of 7-and 8-year-old users has jumped from 9% in 2001 to 14%, a study by Mintel showed last year. Among 9- and 10-year-olds, a third owned phones, up from 16%. For children aged 11 to 12 and 13 to 14, the proportions with cell phones were 73% and 87% respectively.

Mr. Stewart’s independent expert group reported in May 2000 that there were no adverse effects for the general public, but said that children should only use cell phones for essential calls.

The report called for information leaflets on cell phones and health to be delivered to every household and that emission levels, known as SAR values (specific absorption rate) should be displayed on packaging, as a menu option in the screens, on the phone itself and on a national Web site.

Reiterating his demand for more public information, Mr. Stewart said: “The man in the street must be able to get information on radiation levels readily and easily.

“Take the information on the [industry] Web sites. It has been said that to find out SAR values you need to be a computer operator to get to it, a physicist to understand it, and to have a Ph.D. to analysis it effectively.”

Asked whether he was more or less concerned about the possible risks of health dangers linked to cell phones than five years ago, Mr. Stewart replied: “I am more concerned.”

A professor of epidemiology at the Karolinska Institute in Stockholm, Anders Ahlbom, published a study in October suggesting that those who had used cell phones for 10 years were almost twice as likely to develop an acoustic neuroma, a tumor on a nerve connecting the ear to the brain, compared with shorter-term users.

Other studies have concluded that there are no risks from the technology. The English government and industry are jointly funding a series of studies as part of that country’s $14 million Mobile Telecommunications and Health Research program.

The radiation protection board’s report called for an independent review of planning procedures for cell-phone towers. Mr. Stewart said: “Some local authorities have little expertise and consultation with communities is variable.” He also recommended the monitoring of exposure from the newer third-generation, or 3G, transmitters and those for the police’s new terrestrial trunked radio (Tetra) system.

A professor of electrical and computer engineering at Utah University, Om Gandhi, has published research suggesting that children’s brains absorb 50% more radiation from hand-sets than adults. He said the absorption rate for an adult was 2.93 W/kg, 3.21 for a 10-year-old, and 4.49 for a 5-year-old.

Mike Dolan, of the Mobile Operators’ Association, said: “The key point of the radiation protection board advice is that there is no hard evidence linking the use of mobile telephony with adverse health effects.”

The Department of Health said: “Our advice is that all under children under the age of 16 should use a precautionary approach.”