A new research has indicated that using a mobile phone for just 15 minutes a day can substantially increase the risk of brain cancer among its users.
A series of studies across 13 countries found that the longer people used their mobile, the higher was the risk.
Elisabeth Cardis, leader of the Interphone Study, said an increased risk of brain tumours, known as gliomas, was seen in the 20 per cent of users with the highest exposure to radio-frequency emissions.
She said there was an increased risk of brain cancer close to where users held the phones to their heads.
Those who had used handsets for 15 minutes a day for seven years, showed a 72 per cent higher incidence of gliomas.
Gliomas are fatal, usually within three to five years of diagnosis, even with treatment.
"This research shows that heavy users are at the biggest risk and that there is a very high increase in the risk of brain cancer from just 15 minutes of mobile phone use. Fifteen minutes is really not that long any more," the Daily Express quoted Graham Lamburn, technical manager at independent watchdog Powerwatch, as saying.
"Many people use their phones for much longer than that each day now. If the indications in this study are right ... then this is a potential timebomb," added Lamburn.
The research comes just two weeks after the World Health Organisation warned for the first time that mobile phones may cause cancer, urging phone owners to limit their use.