Researchers at the Swedish National Institute for Working Life have studied 2,200 mobile phone users and found an increased risk of brain tumours in mobile handset users.

The study found a 240 per cent increased risk of a malignant tumour on the side of the head where the phone is used, and the earlier the patient starts using a mobile phone the higher the chances of a serious illness.

The study (PDF) looked at digital and cellular phones as well as cordless landline handsets.

"This pooled analysis showed consistently increased risk for malignant brain tumours using >10 years latency period," said report authors Lennart Hardell, Michael Carlberg and Kjell Hansson Mild.

"Especially high odds ratio was found for high-grade astrocytoma. Odds ratio increased with cumulative lifetime number of hours of use of analogue and digital cellular telephones and cordless phones. In multivariate analyses increased risk was found for all three phone types."

The findings contradict several earlier reports on the relative safety of mobile phones. A UK university study earlier this year cleared mobile phones for use, but did find a preponderance of tumours on the side of the head most used for calls. 

Another study, finished last year, concluded that there was no danger but pointed out that long term use may have more serious side effects.