Health experts have called for a halt to adding fluoride to drinking water amid claims it could give people bone cancer.

The chemical has been added to water supplies covering six million people in the UK for more than 40 years and the process is backed by Public Health England who say it is a 'safe and effective' health measure to combat tooth decay.

But researchers are now saying it may cause seriously dangerous side effects such as bone and bladder cancers and also lower children's IQs.

Fluoride is added to the water supply of 6m Britons in an effort to fight tooth decay (file picture)

Prof Stephen Peckham, of the University of Kent, pictured, has called for a halt to fluoridation

Stephen Peckham, professor of health policy at the centre for health service studies at Kent University, said the process was introduced before there was enough research to demonstrate its safety and effectiveness.

He told The Guardian: 'It's a dental health policy that's got up a head of steam and people have been reluctant to see it criticised.

'You can't really confidently say that water fluoridation is either safe or effective. There is a problem where the evidence is seen as either totally in favour or totally negative and it's more murky than that.'

Prof Peckham has led research into whether hyperthyroidism - which can cause anxiety, sleeping problems and muscle weakness - is linked to fluoridation but said there are problems with evidence on both sides of the argument.

He added he wanted to see the process stopped and a study set up to see its effects on children in fluoridated and non-fluoridated areas.

It comes after the Cochrane Collaboration, an organisation of 14,000 academics, reviewed fluoridation evidence earlier this year - but they too failed to come to a conclusion.

The researchers found data showed there was some effectiveness in reducing tooth decay but that the only studies deemed admissible were from before 1975 and the risk of bias was high.

'Supervised tooth brushing' is another recommended method to fight tooth decay (picture posed by model)

Britain is one of few countries in the world that allow fluoridation schemes, where it is aimed to deliver 1mg of the chemical per litre.

In contrast, the US this year reduced the level of fluoride in its water to 0.7mg per litre.

But Public Health England continues to back the scheme and has said it is a 'safe and effective measure'.

The government body said fluoridation was one of a range of actions it promoted to battle tooth decay, with others including supervised brushing.