Alan Johnson, the Health Secretary, has been accused of overstating the benefits of adding fluoride to water in the fight against dental disease.

Tooth decay in children across Europe has fallen irrespective of whether there is fluoride in the water, authors of a report have said.

Mr Johnson has called for it to be added to all water supplies in the United Kingdom in an attempt to reduce the number of people seeking dental treatment.

He said children in Manchester, where water is not fluoridated, were twice as likely to have tooth decay as those in Birmingham, where it is added.

Mr Johnson said a review of evidence by York University had found that adding fluoride reduced the number of children with tooth decay by 15 per cent.

But the authors said their findings have been used selectively and the impact of adding fluoride to water supplies was unclear. They accused the Government of giving "an over-optimistic assessment of the evidence in favour of fluoridation".

"The Department of Health's objectivity is questionable," said Sir Iain Chalmers, the editor of the James Lind Library in Oxford, and Prof Trevor Sheldon, the deputy vice-chancellor at York University, who conducted the review.

They said tooth decay in 12- year-olds has reduced across Europe irrespective of whether there is fluoride in the water.

The countries with the biggest drop in childhood tooth decay - Sweden, Netherlands, Finland and Denmark - do not fluoridate the water.

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