Image caption Mobile phone safety has been much debated over the past two decades

Further research has been published suggesting there is no link between mobile phones and brain cancer.

The risk mobiles present has been much debated over the past 20 years as use of the phones has soared.

The latest study led by the Institute of Cancer Epidemiology in Denmark looked at more than 350,000 people with mobile phones over an 18-year period.

Researchers concluded users were at no greater risk than anyone else of developing brain cancer.

The findings, published on the British Medical Journal website, come after a series of studies have come to similar conclusions.

'Reassuring'

But there has also been some research casting doubt on mobile phone safety, prompting the World Health Organization to warn that they could still be carcinogenic.

In doing so, the WHO put mobile phones in the same category as coffee, meaning a link could not be ruled out but could not be proved either.

The Department of Health continue to advise that anyone under the age of 16 should use mobile phones only for essential purposes and keep all calls short.

These results are the strongest evidence yet that using a mobile phone does not seem to increase the risk of cancers of the brain or central nervous system in adults Hazel Nunn, Cancer Research UK

The Danish study, which built on previous research that has already been published by carrying out a longer follow-up, found there was no significant difference in rates of brain or central nervous system cancers among those who had mobiles and those that did not.

Of the 358,403 mobile phone owners looked at, 356 gliomas (a type of brain cancer) and 846 cancers of the central nervous system were seen - both in line with incidence rates among those who did not own a mobile.

Even among those who had had mobiles the longest - 13 years or more - the risk was no higher, the researchers concluded.

But they still said mobile phone use warranted continued follow up to ensure cancers were not developing over the longer term, and to see what the effect was in children.

Hazel Nunn, head of evidence and health information at Cancer Research UK, said: "These results are the strongest evidence yet that using a mobile phone does not seem to increase the risk of cancers of the brain or central nervous system in adults."

Prof Anders Ahlbom, from Sweden's Karolinska Institute, praised the way the study was conducted, adding the findings were "reassuring".

Prof David Spiegelhalter, an expert specialising in the understanding of risk who is based at the University of Cambridge, said: "The mobile phone records only go up to 1995 and so the comparison is mainly between early and late adopters, but the lack of any effect on brain tumours is still very important evidence."

And Prof Malcolm Sperrin, director of medical physics at Royal Berkshire Hospital, said: "The findings clearly reveal that there is no additional overall risk of developing a cancer in the brain although there does seem to be some minor, and not statistically significant, variations in the type of cancer."

But the researchers themselves do accept there were some limitations to the study, including the exclusion of "corporate subscriptions", thereby excluding people who used their phones for business purposes, who could be among the heaviest users.