There are more than one billion mobile phone users worldwide.

Longer follow-up is needed to check that health problems do not arise with many more years of use, the researchers say in the British Journal of Cancer.

An independent group for the UK government, led by Sir William Stewart, that looked into the safety of mobile phones in the late 1990s also concluded mobile phones did not appear to harm health.

However, the group said there was evidence that radiation from mobile phones could potentially cause adverse health effects, and therefore a "precautionary approach" to their use should be adopted.

Precautions

The government currently advises mobile phone users to keep their call times short.

And children under the age of 16 should use mobile phones for essential calls only, because their head and nervous systems may still be developing.

The latest data from the UK, Denmark, Finland, Norway and Sweden, included 678 people with acoustic neuroma and 3,553 without this form of cancer.

This revealed no relation between the risk of acoustic neuroma and the number of years for which the mobile phones had been used, the time since first use, total hours of use or total number of calls.

You can also check : Top News News of the Week

Nor was there any link with analogue or digital phones or whether or not a hands-free kit was used.

On balance, the evidence suggests there is no substantial risk of acoustic neuroma in the first decade of use - but the possibility of some effect after longer periods remains open, the researchers concluded.

Senior investigator Professor Anthony Swedlow said: "Whether there are longer-term risks remains unknown, reflecting the fact that this is a relatively recent technology."

Dr Michael Clark from the Health Protection Agency said: "This is good news but we still need to be a bit cautious."

Dr Julie Sharp, senior science information officer at Cancer Research UK, said: "This study provides further evidence that using mobile phones does not increase the risk of brain tumours.

"However, it is important that researchers continue to monitor phone users over the coming years as mobiles are still a relatively new invention."

The research is part of a bigger study that will be published next year.

A Swedish study identified an increased risk of acoustic neuromas among people who had used mobile phones for 10 years or more.

People have been concerned that the radiofrequency from phones might cause cancers, despite the absence of a known biological mechanism for this.