But they said they could not rule out longer-term risks, as mobile phones remained a relatively new technology.

Acoustic neuromas are benign tumors which grow in the nerve connecting the ear and inner ear to the brain, close to where mobile phones are held to the head.

Damage to the Immune System?

Fears that using mobiles can cause cancer have existed since the mid 1980s when they first became popular.

Particular concerns have existed over the potential harm that could be done to children, whose brains are still developing.

One Welsh scientist, Roger Coghill, campaigned for health warnings to be attached to mobile phones. In 1998, he even took one retailer in Cwmbran to court because it refused to carry such warnings on its phones.

Coghill, who specializes in bio-electromagnetics, claims mobiles are linked to headaches, memory loss and can damage the immune system.

He claims radiation emitted by mobile phones damages the body's electromagnetic fields, and that the microwaves they generate damage the ability of white blood cells to fight off infections.

Concerns Grossly Exaggerated

The new study, published online in the British Journal of Cancer, was carried out in the UK, Denmark, Finland, Norway and Sweden -- countries where mobile phones were introduced particularly early.

Data was collected from 4,231 people, 678 of which had acoustic neuroma. Acoustic neuroma can cause hearing loss and difficulties balancing, but is usually slow-growing and does not spread to other parts of the body.

The researchers found no link between acoustic neuroma and the number of years mobiles had been used or the total hours of use. They also found no link between analog or digital phone use.

Dr. Paul Walker, chair of the Public Health Alliance Cymru, said phone users were unnecessarily concerned about the risks, which are grossly exaggerated.

"People worry about technology they don't understand. It's easy to think it can be dangerous but all we know about the effects of radio waves are that they cause slight heating of the brain which has not been known to cause a great deal of difficulty."

No Substantial Risk in First Decade

But the researchers said that there was relatively little information for the risk of tumors after phone use for 10 years or more.

Senior researcher Professor Anthony Swerdlow said, "Our results suggest there is no substantial risk in the first decade after starting use. Whether there are longer-term risks remains unknown, reflecting the fact that this is a relatively recent technology."

Around one billion people worldwide use a mobile phone.

Youngsters are thought to be at higher risk from mobile phone radiation because their nervous system is still developing so they absorb more energy though their head and are likely to be exposed to emissions for more years.