Southampton councillors have voted to oppose controversial plans to fluoridate to the city's water supplies.
By a majority of around 2-1, city councillors backed a motion opposing the addition of fluoride to tap water to fight tooth decay.
And councillors agreed to use any future powers the authority may be given to prevent the implementation of a proposed fluoridation scheme by health chiefs.
Under the Government's proposed NHS reforms, councils are due to be handed powers over fluoridation schemes when strategic health authorities (SHA) are scrapped in 2013.
Opponents of the proposed Hampshire scheme gathered a 6,000 name petition to force Southampton City Council to debate a motion on withdrawing its backing for fluoridation.
Hampshire Against Fluoridation sent an open letter to all 48 elected officials urging them to vote to oppose adding the chemical to tap water.
South Central SHA is working with Southern Water to determine how fluoride will be added, after defeating a High Court legal challenge.