Alan Johnson’s attempt to extend water fluoridation across England is likely to focus on the most deprived 20 per cent of the population, which experiences 80 per cent of the nation’s dental disease.
Dentists say that in countries where water fluoridation is widespread, such as America, Australia and New Zealand, dental health is far superior to this country’s.
It is also better in those parts of the country where the water is treated compared with those where it is not.
In a letter sent by Prof Raman Bedi, the chief dental officer for England, to health chiefs two years ago, he referred to the “duty” of primary care trusts to reduce health inequalities.
But these areas of need rarely coincide with the boundaries of water companies, and partial fluoridation can pose technical difficulties.
There are legal procedures that need to be followed if health chiefs are to instruct water companies to fluoridate their supplies.
Under regulations introduced in 2005, health authorities are expected to carry out a public opinion survey, set up focus groups and consider all letters and resolutions.
The Department of Health has already drawn up a “model agreement” covering the main terms to be included in any arrangements between England’s 28 strategic health authorities and the water companies.
They can go ahead with a scheme if they are “satisfied that the health arguments in favour of proceeding with the proposal outweigh all arguments against proceeding”.
Anti-fluoride campaigners say that the science is unproven and that fluoridation poses significant risks to health.
Critics also claim that fluoridation is “indiscriminate mass medication”, and should not be forced on people against their will through their water supply.
Supporters say the biggest argument in favour of water fluoridation is that it works. Although a large group of people mistakenly believes its supplies are fluoridated, only a small part of England is covered by schemes, principally around Birmingham and eastern England.
The last major battle over fluoridation was in the North East in the early 1990s, when health authorities, backed by 70 per cent of the local population, had a scheme that would have covered one million people rejected by Northumbria Water, and the courts.
Under the 2003 Water Act, the 28 strategic health authorities now have the final say over whether fluoride should be added to the supply. That overturned a 1985 ruling that effectively left the decision up to the water companies, which were reluctant to fluoridate for fear of being sued and did not want responsibility for public health decisions.
Fluoride is present naturally in virtually all water supplies but most levels fall short of the optimum for dental health, which is one part per million.
For years ministers have wanted to see fluoridation expanded beyond the six million people currently covered by natural and artificial schemes