A proposal for Wellington City Council to oppose the airport's expansion plans has been voted down.

A notice of motion, filed by councillor Iona Pannett and seconded by deputy mayor Sarah Free, was considered over the course of two hours at a council committee meeting this morning.

They wanted the council to oppose the expansion unless Wellington International Airport and airlines reduce their carbon emissions, improve air quality, reduce air traffic noise, and reduce the use of private vehicles to and from the airport.

Council officials did not support it on the grounds it presented a risk to both the council's regulatory function and its commercial relationship with the airport.

Officials obtained specialist legal advice, which Pannett said she has not been granted access to, that said the move could be unlawful.

That's because the wrangle has played out against the backdrop of Environment Court proceedings, in which the council is party to in its role as a regulator.

Local lobby group Guardians of the Bays has lodged an appeal against the airport, after it got initial approval to turn a green space to the east of the building into tarmac.

A panel of independent commissioners appointed by the council made the recommendation for this approval.

"In agreeing to this Notice of Motion Councillors would be seeking to override that regulatory decision, despite not having the same level of specialist expertise, or considering the evidence or submissions", council officials warned.

Pannett acknowledged the council had a number of roles, which she said included being a policy maker and a strong advocate for the city on climate change.

"We need to take a stance on the airport's master plan."

Advice given during the committee meeting was that passing the notice of motion in itself would not reduce carbon emissions.

Mayor Andy Foster said the move wouldn't achieve anything, other than damaging the council's reputation.

Councillor Fleur Fitzsimons said she would have been more supportive of an approach that actually led to a substantive outcome.

"But I really don't think it's appropriate or helpful to anyone for us to insert ourselves in this process at this time, however well-meaning the intention is."

Councillor Jenny Condie said the notice of motion should have been a media release.

"Instead we've had this notice of motion that's taken 50 hours of our chief lawyer's time and probably has cost us, I would guess, $10,000 to prepare this report and bring it to us."

The reality was the council did not have many levers to pull on aviation emissions, Condie said.

The airport said it was "nonsensical" for the council to consider opposing its plans, given the council's regulatory role in recommending the designations be confirmed.

The airport argued it was already taking action on all of the points the notice of motion outlined, including carbon emissions from both the airport terminal and airlines.

"Our progress is real, as demonstrated by the first electric flight to land in Wellington last year. This demonstrates that the technology to decarbonise air travel is right on our doorstep."

The airport stressed its proposed expansion work did not currently include extending the runway.

Guardians of The Bays spokesperson Dr Amanda Thomas said sustainable fuels for aviation did not exist at scale and would not in sufficient time to address the council's emission reduction plans.

"There's no indication that the technology is going to save us. More passengers mean more emissions. As hard as it is, we do have to set about reducing demand."

Guardians of The Bays has consulted two lawyers who advised the notice of motion was not unlawful and had no legal implication.

How councillors voted

For: Laurie Foon, Sarah Free, Teri O'Neill, Iona Pannett, Tamatha Paul

Against: Andy Foster, Diane Calvert, Jenny Condie, Jill Day, Fleur Fitzsimons, Rebecca Matthews, Simon Woolf, Nicola Young, Liz Kelly

The situation comes as the latest spat between the council and the airport after councillors pulled the plug on $76 million set aside in its Long Term Plan for "airport seawalls".

The airport, which appeared bewildered by the move last year, said councillors had conflated the seawall project with plans to extend the runway.

In October, councillors considered a proposal to sell the council's 34 per cent share in the company, but that was voted down.

The same left-leaning councillors leading the charge on the current notice of motion to oppose expansion plans are also vehemently opposed to asset sales.