While the benefits of fluoride for preventing tooth decay are generally accepted, some studies have claimed it increases the risk of bone disease.

But the latest research, centred on Hartlepool, a town with naturally high fluoride in water, says other factors are more relevant in dictating the risk of fractures.

Our findings suggest that concerns about a possible risk of hip fracture should not be a reason for withholding fluoridation of water supplies

Professor David Coggon

Scientists at the Medical Research Council (MRC) at Southampton University allowed for other factors such as poor nutrition and concluded that being underweight or doing little physical activity were responsible for increased risk.

Around 10% of water supplies in the UK are fluoridated.

The MRC researchers said increased fracture rates could not be blamed on concentrations of fluoride at levels found in water supplies, even when additional fluoride was added.

The level of concentration in water had a "negligible effect" on people's uptake of the fluoride ion - responsible for increased risk of fractures, they said.

There was no difference in the chance of hip fractures for those people looked at in the study regardless of how long they had been exposed to higher fluoride levels.

Professor David Coggon and his team looked at the cases of 914 hip fracture patients and 1196 people, also from the Hartlepool area, who had not suffered from the condition, reports the medical journal The Lancet.

He said: "Our findings suggest that concerns about a possible risk of hip fracture should not be a reason for withholding fluoridation of water supplies."

'Compelling evidence'

Commenting on the findings, Dr Clifford Rosen, of the Maine Center for Osteoporosis Research and Education, said in The Lancet that they amounted to "compelling evidence" that fluoridation did not increase the risk of fractures.

But he added: "The controversy is likely to continue, as water fluoridation becomes more widespread, osteoporosis in the general population increases, and more case-control studies in larger cohorts are undertaken."

Water UK, which represents all the country's water suppliers, said it was up to local communities to decide whether it wanted its water supplies to be fluoridated.

Health authorities can ask for fluoride to be added to water but the supplier has the final say. Since 1985 only one request out of a total of 56 has been granted.