Ministers plan a big expansion in the fluoridation of tap water, believing that proven benefits to dental health outweigh civil liberties objections and the possibility of increased medical risk.
They want strategic health authorities in England and Wales to be more determined in insisting that fluoride is added to water supplies where there is clear local support.
Amendments to the Water bill, which will be debated in the Commons this month, will strengthen the hand of health bodies. Existing legislation says authorities may ask water companies to add fluoride, and some backbenchers want this to be changed to an obligation where there is support.
There may be a free vote on the issue, since it might be argued there is an ethical dimension over what critics will see as "compulsory medication".
Ministers indicated their support for more fluoridation in September when they argued that a review of evidence by the medical research council showed no reason not to pursue fluoridation on public health grounds.
The Sunday Times yesterday published extracts from a letter written by the health minister Hazel Blears and the environment minister Elliot Morley to John Prescott, the deputy prime minister, in his role chairing the domestic affairs cabinet committee.
These said: "Those who remain adamantly opposed would be able to use water filters that remove fluoride or buy bottled drinking water. Experience of oral health promotion projects shows that it is much harder to establish regular tooth-brushing in deprived areas because of the costs of toothpaste and, perhaps, because of the less ordered lifestyles lived by families."
The letter added that opponents were in a minority which "should not be allowed to deprive health communities from opting for fluoridation by insisting on an indefinite research programme".
The Department of Health said yesterday: "The government will be encouraging health authorities with particular dental health problems to consider fluoridating their water as part of their overall oral health strategy."
About 5million people in England already have fluoride in their tap water in Birmingham, the West Midlands and on Tyneside, while another 500,000 from Hartlepool to parts of Essex have naturally fluoridated water.
A Commons early day motion obliging water companies to fluoridate water, where a clear majority of local people want it, has the support of 136 MPs.
Andy Burnham, the Labour MP for Leigh, Greater Manchester, who tabled the motion, said yesterday: "For far too long a vocal minority have been allowed to stand in the way of a change that would benefit millions of children in this country.
"In Greater Manchester on average children under five have 2.5 missing, filled or decayed teeth, in the West Midlands it is less than half. I think we have pussy-footed around for far too long."
Jane Jones, campaign director of the National Pure Water Association, which campaigns against fluoridation, said: "This is nanny statism. To medicate the whole population against their will is not the way to deal with tooth decay."
Water companies have argued that, though they could add more fluoride, the decision to do so must be a political one. The medical research council report said there was a need for more information on exposure to fluoride, particularly in children who would be more likely to swallow toothpaste, and on the discolouring of teeth.
