The airport, New Zealand's largest, has a market value of about NZ$13 billion ($8.25 billion), meaning the city's stake is currently worth about NZ$2.4 billion. It is the airport operator's biggest shareholder.

Auckland Mayor Wayne Brown said in a statement that the sale would permanently improve the city council's financial position, helping it to fill a $325 million budget shortfall and avoid service cuts.

In the financial year ended June 30, 2022 the city had NZ$11.1 billion of debt, a figure that is expected to have increased in the current year.

An AIA spokesperson said in an email that the company had no concerns about the proposed stake sale, which would not affect day-to-day operations, and it was up to investors to make their own decisions. The airport does not expect to be involved in any sales process, the spokesperson added.

Under the mayor's proposal, local government taxes, known as rates, would only increase by 6.7%, which is in line with New Zealand's inflation rate, and other services in the city would not have to be cut.

"It makes absolutely no sense to retain those shares when we could realise the capital gains and wipe NZ$2 billion of debt from the council books for good. The savings from that are huge," Brown said. "If we don't sell now, we'll have to put rates up by double-digits and make bigger cuts."

The plan needs majority approval from the city's elected council members at a vote set for June 8 and it is not guaranteed to pass.

Council members who oppose the sale of the airport stake have noted it traditionally provides significant annual revenue to the city through dividend payments.

Councillor Alf Filipaina told Radio New Zealand that he was opposed to the sale because profits made by the airport would not go back into the community.

($1 = 1.5763 New Zealand dollars)

(Reporting by Lucy Craymer; Editing by Jamie Freed)

By Lucy Craymer