ACUSHNET — In a move to block New Bedford from fluoridating the water supply, selectmen voted unanimously last night to ask town counsel about taking legal action against the city, and are trying to enlist Fairhaven’s and Dartmouth’s support in the ensuing fight.

“Does New Bedford not have any responsibility to Acushnet and Dartmouth just because 100 years ago they bought some drinking water rights in Lakeville?” said Selectmen Chairman Robert F. Brown.

Acushnet, Fairhaven and Dartmouth, as well as a part of Freetown, secure some or all of their drinking water from the city.

Acushnet officials and residents have been opposed to fluoridation, questioning its effectiveness and maintaining that it hasn’t been proven that its health benefits outweigh the risks.

Town voters in a non-binding resolution at the Oct. 17 Special Town Meeting nearly unanimously rejected the proposal to fluoridate the municipal water purchased from New Bedford.

However, a city ballot initiative taken Nov. 7 was binding and equipment has been purchased to start fluoridation Friday.

Selectmen voted 3-0 last night to ask Kopelman and Paige, the town counsel, if a Bristol Superior Court injunction is a possible legal avenue to take against New Bedford.

Town Administrator Alan Coutinho will also contact selectmen in Fairhaven and Dartmouth to see if they will support legal action on the fluoride front.

“We should ask Dartmouth and Fairhaven to see if they would support a joint venture to stop fluoridation,” Mr. Brown said.

Selectman David E. Wojnar injected a cautionary note. He said Acushnet does not have much leverage — if any — in going up against the city.

“They could tell us to go buy bottled water,” he said.

But Selectman Michael Cioper said any delaying action on the fluoride front might give the town the time needed to put a question on the April annual election ballot.

“Maybe we could stop it,” he said. “Do we have the power to do that?”

The board voted to forward letters to Fairhaven and Dartmouth, which also buy drinking water from New Bedford. If there is no support, however, Mr. Brown said Acushnet should work with the town’s Board of Health to stop fluoridation after it starts.

“This is a health issue,” Mr. Brown said. “Other towns have determined the health risks outweigh the health benefits and worked to stop fluoridation. I’ll talk with the Board of Health; this should be a coordinated effort.”

Acushnet selectmen in June voted 3-0 to relay their opposition to fluoride to New Bedford Mayor Scott Lang. At the time, the mayor — who has opposed fluoridation but agreed to put the matter before voters — said he was sympathetic to the Acushnet position.

However, he also said the appropriate response was to find other delivery systems.

Acushnet last year had actively been seeking water independence from the city by developing its own resources. That effort was quickly back-burnered, however, when it was determined that water supplies to be tapped would not provide the daily quantity the town would need to end its dependence on the New Bedford supply.

The New Bedford Water Department has an average daily consumption rate of 12.5 million gallons per day.