Mobile phones are at the centre of new safety fears after scientists found the first evidence of a link with brain cancer.
Users who spend more than an hour a day talking on a cell phone are almost a third more at risk of developing a rare form of brain tumour, a study has found.
The cancers were found most frequently on the side of the head to which the phone was held.
Scientists found the cancer link with digital mobiles, old- style analogue mobiles and digitalenhanced cordless phones.
The findings, published in the International Journal of Oncology, will renew health concerns among Britain's 47million mobile users.
One expert said yesterday that another large-scale study would be needed to confirm the apparent link.
Radiation from mobile phones has been shown to alter the workings of brain cells and affect memory.
But the biggest British study three years ago, led by the Government's former chief scientific adviser Sir William Stewart, found that there was no evidence of a risk to human health.
A report by the American National Cancer Institute in 2001 also failed to find a link between mobile phone use and brain cancer.
The latest findings are the first to show a link between the instruments and disease in humans.
In the study, lead researcher Professor Kjell Mild examined the medical records of 1,600 tumour victims who had been using mobile phones for up to ten years before diagnosis.
Professor Mild, a biophysicist at Orebro University in Sweden, said the evidence was clear: 'The more you use phones and the greater number of years you have them, the greater the risk of brain tumours.'
Scientists compared tumour sufferers with a control group who led similar lives but did not use mobile phones.
They also compared sufferers with tumour victims who did not use mobile phones.
The study found that spending more than an hour a day on the phone increased the risk of a type of tumour known as acoustic neuroma by 30 per cent.
Such tumours occur in one of the nerves in the brain and can lead to deafness in one ear.
They are usually curable by surgery.
Although the cancer is rare, say numbers have increased from one tumour per 100,000 people in 1980 to about one per 80,000 today.
Dr Richard Sullivan, head of clinical programmes at Cancer Research UK, said: 'These latest findings appear to show a link and that warrants further investigation.
'We would need to see a large-scale study replicating these results before we could say whether they are significant.
'Certainly the study appears to be robust.'
The National Radiological Protection Board said in a statement that it considers mobile phones safe in relation to cancer.
'Radio waves do not have sufficient energy to damage genetic material in cells directly and therefore cannot cause cancer.'