After talk of herding cats, swallowing dead rats, weddings, funerals and even King Solomon, Christchurch City Council has chosen to keep its current city boundaries and take on Environment Canterbury's functions.

Councils have until Sunday to come up with their own Head Start plans for reorganising their boundaries under proposed local government reforms, or the decision will be made for them.

The majority of Christchurch's councillors rejected an option to join with urban areas of Selwyn and Waimakariri to form a super city and instead opted to go it alone.

The decision comes after Christchurch's councillors [https://www.rnz.co.nz/news/politics/883755/christchurch-city-council-reluctantly-agrees-to-take-part-in-reform-of-council-boundaries reluctantly agreed on Tuesday to take part in the government's Head Start process].

The greater Christchurch metro option that included Rangiora, Rolleston and other towns in the neighbouring districts was favoured by Mayor Phil Mauger but lost by one vote.

The seven Labour-aligned councillors along with independents Andrei Moore and Celeste Donovan voted against the proposal.

Mauger said he still believed Christchurch would have been better off with a larger area, but the decision was democracy in action.

"I just still felt it was the right thing to do but, as it turned out, the council aren't behind me so I'm not losing any sleep over it. The council made the decision and we're head down and get on with it."

Amalgamation with the regional council would take "a hell of a lot of time and effort" but the most important thing was the council had agreed to take part in the Head Start process, as the alternative would be drawn out and forced upon them, he said.

Councillors voiced concerns about the costs associated with amalgamation at a Wednesday meeting, as well as the effect on rates and the perception of change being forced on Selwyn and Waimakariri, rather than working with them voluntarily.

Selwyn District Council voted to keep its boundaries and become a standalone unitary authority, and Waimakariri was yet to make a final decision.

Deputy Mayor Victoria Henstock said joining with Selwyn and Waimakariri's urban areas was the best way to support the long-term growth of the region.

"One of the messages that's been consistent throughout this process is that our governance should reflect how people actually live, how they work and how they travel across the region and not how the boundaries were drawn decades ago and the evidence demonstrates that greater Christchurch already operates as a single economic system with Christchurch at its centre and our governance should reflect that reality."

Councillor Melanie Coker said a forced amalgamation with the urban parts of neighbouring regions was nothing but a "hostile takeover".

"This is not the desired outcome in either of those communities through consultation, nor the decision of those two respectful councils or their mayors. In my view, after the mention of dead rats yesterday, to swallow up Rolleston, Lincoln, Rangiora, Kaiapoi would be akin to forcing a dead rat down the throats of our nearest neighbours."

Councillor Andrei Moore said "thank you but no thank you" to amalgamation with neighbouring councils.

Christchurch had "a whole lot of work to do within our own city boundary" before it could be ready to take on others, he said.

"Who the hell is actually going to pay the cost of merging councils? It'll cost an astronomical amount and it appears as though all that cost will fall on ratepayers which people can't afford."

Councillor Nathaniel Herz Jardine said the decision reminded him of the judgement of King Solomon who ordered, when faced with two women who claimed to be the mother of a child, that the baby be cut in half.

"Solomon's purpose in doing this was to find out who was the person who cared the most about the baby and would say 'no, let's not cut it in half'."

The council had been given the option to consider its values and decide on its priorities in the face of the "grotesque option of cutting in half both of our neighbours", Herz Jardine said.

The problems the region faced around transport, river catchments, urban planning and rates would not necessarily be solved by swallowing up neighbouring urban areas and leaving the rural parts on their own, he said.

Councillor Tyrone Fields said he wore a tie to the meeting because he did not know if he was going to a wedding or a funeral.

He was "absolutely convinced" Christchurch becoming a unitary authority within its existing boundaries was what was best for the city and made more sense than trying to "swallow up the urban parts of Selwyn and Waimakariri" against their wishes.

"Relationships where one side says 'no thanks' generally don't end well."

Fields said it was "incredibly ironic" that a government elected on reducing bureaucracy had decided that the answer was "a massive bureaucratic restructure".

"That is bonkers," he said.

Councillor Kelly Barber said the meetings he had attended about the amalgamation process felt like herding cats and it was difficult to reach a consensus with so many different factors at play.

Christchurch was a natural fit with its urban neighbours from Rangiora, Kaiapoi, Rolleston and Lincoln and there was clear evidence the centres were inextricably linked and already operated as a single economic unit, Barber said.

"We have far more in common than we don't," he said.

Councillor David Cartwright said parts of the experience had felt like chewing tinfoil.

It was an expensive exercise forced on the council by central government and the decision made by elected members would affect everyone in Canterbury, he said.

As part of the Head Start process the council would have to consider what community boards, rates levels, water charges and transportation would look like, Cartwright said.

The urban areas of Selwyn and Waimakariri would continue to grow and it made sense for them to be one with Christchurch, he said.

Cabinet is expected to make a decision on Head Start proposals with the aim of having new unitary councils elected in October 2028.

-RNZ and Allied Media