Photo: © 2010 AP via AAP/PETROS KARADJIAS

The decade long, $27 million study was backed by the World Health Organisation as well as phone companies, which were contractually bound not to interfere with the independence of the results.

The study found no increase in brain tumours over the past decade and was unable to establish a direct link between phone use and cancer.

However it did find that when heavy mobile users did develop tumours, they were most likely to occur on the side of the head they regularly use to take and make calls. 

One of the scientists behind the study, Sydney University's Dr Bruce Armstrong, says the results are inconclusive and more investigation is still needed.

"We still can't say with confidence that there's no issue with respect to brain tumours and mobile phone use," he told the Sydney Morning Herald.