Proposed changes to local government law will lead to amalgamation by stealth, councils say.
The organisation representing councils, Local Government New Zealand, has been told by 97 percent of its members to oppose so-called undemocratic measures in a Bill to amend the Local Government Act.
If the Better Local Services Bill passed, it would give the Local Government Commission the power to create council-controlled organisations without seeking the agreement of councils or the community.
The organisations would become responsible for the day-to-day management of basic services, and councils would become shareholders, purchasing the services back.
Councils had mounted an intense public campaign in response.
Over the weekend, Invercargill city councillors published a full-page ad in The Southland Times, urging Southlanders to unite against the proposed changes.
Invercargill Mayor Tim Shadbolt said the government needed to be honest about what its intentions were.
Local Government Minister Sam Lotu-Iiga had given him assurances in April that forced amalgamations would not happen, but he was not convinced.
"My message would be, look, just be honest with us so we can talk about it," Mr Shadbolt said.
"What are you trying to achieve? If it's better efficiency, you show me a system anywhere in the world that provides as much fresh water as you like for 86 cents a day - that's what everyone in [Invercargill] pays."
The changes in the Bill were "sneaky", he said.
"It took a while for our staff to dig out the implications of it because it's buried in a sort of War and Peace-type manual - there's so much detail."
Waimate District mayor Craig Rowley said communities would not have a say in the process and that was undemocratic.
"It's not clear in the legislation what the checks and balances are, and they need to make sure they put the community consultation back into the legislation to make sure the ratepayer's aware of what's going on within their councils," he said.
Local Government Minister Sam Lotu-Iiga said claims there would be no consultation were wrong.
"Votes aren't necessary in some circumstances but where there will be major transactions there will be a vote, there will be a poll," he said.
"But in the ordinary course of working together, there will be a consultation with the public and consultation with those councils, and then it will come back to the Minister to sign off on those."
Submissions on the Bill were being considered by select committee.