Wellington Airport is seeking an urgent meeting with the councillors after it accused them of making a decision based on the "wrong information".
In a Long-Term Plan committee meeting today, the council finalised its budget for the next 10 years which will now go to public consultation.
The marathon meeting which began at 9.30am and continued well past 4pm included a number of last-minute amendments.
One of those was a proposal from Councillor Tamatha Paul to remove a $75 million loan to the airport.
The description for the loan was that it would go towards building a new seawall, but some councillors and community groups believed it was a disguise for a runway extension.
The extension has long been a controversial issue for Wellingtonians which for years was held up in legal battles. There has been no consent application for it since one was withdrawn in 2019.
Speaking at the meeting, Paul criticised the lack of transparency.
"We are still very unclear what this funding is for, and I think it's a significant amount of money to expect ratepayers to dish out, without any clarification about what it's for.
"I am very concerned it could still go towards the runway extension.
"In the case it is a seawall, I still have a fundamental problem with the fact that we're using public money to protect an activity that just continues to contribute to the problem in the first place, which is sea-level rise."
The amendment passed eight votes to seven, but the airport said it was "mystified" by the decision.
"They were making a decision basically on the wrong information," Wellington International Airport Limited chief executive Steve Sanderson said.
"They were making a decision on runway extension, when this is clearly about resilience on our seawalls which are some 50 years old, and those seawalls - particularly the western seawall, Lyall Bay - protects first sewage lines and then the road, and then the airport.
"All this money would have contributed towards replacement of that seawall. The councillors do need to go back and re-think their obligation to the sewage lines and the roading."
He said it was disappointing the decision was made without any councillor coming to them first.
"We were a little bit surprised this was going to council today, and I think they would have made a much better decision if they'd come to us first.
"We will be seeking a meeting with councillors. They need to look at the information and they need to put this back on the table."
In response, Councillor Paul said she was herself "surprised" at the airport.
"It's surprising and disingenuous for the airport to claim they are mystified.
"The airport was on notice about this when the council declared a climate emergency. The council and the thousands of Wellingtonians who went on the climate strikes are serious.
"They should be in no doubt of my position on this matter. I remain happy to discuss this further with them."
She said she met just last month with the airport to discuss their expansion plans.