Napier MP Chris Tremain says the three Hawke's Bay mayors opposed to amalgamation are simply "protecting their patch".
But the mayors say they were elected on anti-amalgamation tickets and the proposal to merge the region's five councils should be scrapped.
Conflicting views were expressed in strongly-worded submissions to the Local Government Commission at a hearing in Napier yesterday.
In a joint submission on behalf of Napier City, Wairoa District and Central Hawke's Bay District councils, Wairoa Mayor Craig Little said the commission's amalgamation proposal was "divisive and not the right way forward for our region".
"We actually question why we are even here, given the mandate is clearly not there for the current proposal to go any further - look no further than the submissions against this draft proposal," he said.
Appearing later in the day wearing a Magpies rugby jersey, former local government minister Mr Tremain, who is standing down at this year's election, said amalgamation would "release the handbrake on growth and prosperity" in the region.
"The current model [of local government in the region] does not maximise the opportunities for the province to grow, to enhance services for all of our people from Wairoa to Central Hawke's Bay, and to enhance our environment," he told the commissioners.
While other organisations had seen the benefits of amalgamation "local government has been one of the last to seize the opportunity," he said.
"I do not blame [Hawke's Bay's mayors and councillors] for defending their patch, for defending the status quo. That is in fact the job they were elected to do. My issue is with the structure."
Mr Little told the commission: "We all stood against amalgamation and we were all voted in by the people of our respective regions to fight against it. Yet because we disagree with the opinion of the government and the [pro-amalgamation] Hastings District Council we are accused of being parochial and conflicted."
Speaking to Napier City Council's submission, Mayor Bill Dalton accused the commission of failing to adequately consult on its proposal.
"You have not engaged the community in this process. It is our contention you have simply adopted a proposal made by a very small group in Hawke's Bay. You are using that proposal as your template."
Commission chairman Basil Morrison told Mr Dalton the commission's role under the law was to establish whether there was "demonstrable community support" for the consideration of its amalgamation proposal. It had satisfied itself there was such support.
Mr Tremain called on the commission to specify in its proposal that the mayoral chambers for a merged council would be located in Napier.
Such a move would overcome the perception that amalgamation was "a Hastings takeover" and would have "a profound impact on the goodwill of Napier people towards the proposition," Mr Tremain said.
It would also make sense for an amalgamated council to use the existing "campus" of Napier City Council and Hawke's Bay Regional Council buildings spanning Dalton St in the city, he said.
The commission will continue its hearings of submissions with a session in Wairoa today.
Mr Morrison said it hoped to conclude the hearings process within the next couple of weeks.