The decision-making process was branded “pretty terrible” by a peer who accused health bosses of “misstatements”.
Earl Baldwin’s comments came as members of the House of Lords raised fears over costs, evidence and local consent before any fluoridation takes place.
The peers were discussing proposals which will transfer power over consultations on fluoridation to local authorities, which will be put out to consultation in the new year.
The Government admitted there were “a great range of views” on the matter and insisted decisions should be taken by local councils, not regional health bodies.
Earl Baldwin, a cross-bench hereditary peer, asked Government whip Baroness Northover to set up a neutral body to rule on the evidence next time another city considers fluoridation.
He said: “Some of the misstatements during the Southampton consultation were pretty terrible.”
He went on to criticise Strategic Health Authorities, the regional bodies that were put in charge of deciding whether fluoride should be added to water.
He said: “The problem with the unelected SHAs was – is – that they almost inevitably reflected the dominant medical view.
“Fluoridation was a classic case of premature consensus, on weak evidence from the 1950s and 1960s, and it became a kind of sacred cow, resistant to new evidence.”
The Strategic Health Authority had decided to fluoridate Southampton “against the expressed wishes of its population”, he said, pointing to comments by one expert who described the process as a “religion”.
In September, Southampton city councillors voted to oppose the controversial plans after a campaign by opponents of the scheme forced the matter to be debated in the council chamber.
And they agreed to use any future powers to prevent the implementation of a proposed fluoridation scheme by health chiefs.
After a successful legal challenge, South Central SHA is working with Southern Water to determine how fluoride will be added, after defeating a High Court legal challenge. Nearly 200,000 people in parts of Southampton, Eastleigh, Totton, Netley and Rownhams will be affected by the plans.
Baroness Northover pointed to a study in 2000 that found that adding fluoride to water did decrease the risk of tooth decay.
There were also claims that councils would not be willing to push ahead with fluoridation if they did not get the financial benefits from any improvement in public health.
Labour peer Lord Hunt, the president of the British Fluoridation Society, warned that if local authorities do not have a direct interest in the cost of dental health care, it could be a barrier to them paying out on fluoridation schemes.
But Baroness Northover said councils would be compensated for the costs.