The Westland and Grey district councils, and the West Coast Regional Council have all agreed to one plan. They say having one plan across the region would make consents more "seamless", with one set of rules for everything from mining to housing subdivisions.
However, the Buller council has three times refused to agree to be part of that, expressing fear that it is the first step towards forced council amalgamations.
Yesterday, councillors said 'no' for a fourth time, despite a deputation from the regional council travelling to Westport to press the case.
Buller Mayor Garry Howard today released a letter responding to regional council chairman Andrew Robb: "Councillors have asked that I confirm Buller District Council commitment to work collaboratively together as per the triennial agreement to improve effectiveness and efficiency."
Asked this morning if that was the end of the matter, Mr Howard said they would "always keep an eye on things".
"Never say no."
Mr Robb addressed Buller councillors for about 45 minutes before their meeting yesterday.
He said their concerns were around whether it was the lead into one unitary council for the West Coast.
The cost-benefit analysis had not been done, he said, but be believed that fewer staff would be required in the longer term.
The councils would have committed $25,000 for two years, met dollar for dollar by the Local Government Commission.
