New Zealand First leader Winston Peters says any proposal for a supercity in Auckland should be put to a vote.
Speaking to a public meeting in Takapuna, Mr Peters expressed concern at proposals to replace the region's seven territorial councils with a super council with 20 community councils under its thumb.
A "super-sized Auckland" of 1.4 million people would be the largest local body in Australia and New Zealand, far bigger than Brisbane with one million people, he said.
Mr Peters said those in favour of amalgamation talked about efficiencies, a united voice, one set of bureaucracy, management and leadership for Auckland.
"It sounds great in theory ... [but] has anybody asked you in this hall what you want?
"That is why we are giving you an assurance here and now that we would not go along with any plan to amalgamate one city council with another unless the citizens agree with it. It should be put to a vote."
The Royal Commission of Inquiry on Auckland Governance has spent the year seeking Aucklanders' views, commissioning research and visiting overseas cities to come up with a new local government structure to take Auckland forward for the next 50 years.
It has received more than 3500 public submissions and listened to more than 550 ratepayers, interested parties and councils during two months of public hearings. It will report to the Government by March 31 next year.
Anti-supercity sentiment is strong on the North Shore, with Mayor Andrew Williams telling the commission: "It ain't broke here, so don't try and fix it."
Commission chairman and retired High Court judge Peter Salmon, QC, said the commission had finished seeking information and was sitting down to decide a structure that would best meet the needs of Auckland.
He was speaking after the commission returned from two overseas trip - the first to Melbourne and Brisbane; the second to Vancouver, Seattle, Toronto and London.
Mr Salmon said no city provided an ideal answer for Auckland, but the commission encountered a number of interesting issues. These included an emphasis on sustainable cities, the benefit of integrating migrants from a human and economic perspective, making cities more pedestrian and cycle friendly and moves in Toronto and Seattle to demolish motorways.
"As a generalisation, the cities we visited are no longer investing in accommodating the motor car. They are all promoting and improving their public transport. Even London has decided that no new roads will be built unless needed for regeneration of areas."
Mr Salmon said some of these ideas could end up as recommendations, but acknowledged that implementation would ultimately depend on political will. Another message that was emphasised, he said, was the importance of strong, dynamic and visionary leadership. Coupled with that was the importance of a regional mayor being both a national and international spokesman for a city.
At all the cities visited, the mayors were elected at large. This has been a moot point in Auckland with some councils favouring a mayor elected at large and others favouring a mayor elected among his or her peers.
Asked if the commission would recommend electing a mayor at large, Mr Salmon said: "You will have to wait and see. But there is no doubt that the people we spoke to saw great advantages in a mayor being elected at large ... and I'm pretty confident there was strong support for it [from submitters]. After all, that is what people are used to in New Zealand."