In a day of electoral upheaval, Wellington also elected a Green mayor, Tory Whanau, who upset Labour candidate Paul Eagle.

Kiwis across the country have voted in the local government elections during the past fortnight.

Traditionally fought on highly local issues, the postal elections were optional and produced low turnouts.

However, the shift across much of New Zealand will send an impossible-to-ignore message to the Labour government, and prime minister Jacinda Ardern, who personally endorsed two candidates who suffered heavy losses.

In Auckland, both Labour and the Greens endorsed councillor Efeso Collins, who was trounced by outspoken right-aligned independent Wayne Brown.

Mr Brown, 76, fought off criticism in the campaign's final week after he called a journalist a "pr***" and jokingly vowed to stick pictures of his face on urinals as his first act as mayor.

He replaces the retiring Phil Goff, former Labour leader and foreign minister, as mayor of the city of sails.

In Christchurch, centre-right candidate Phil Mauger will replace another retiring Labour mayor, Lianne Dalziel.

In Dunedin, Greens mayor Aaron Hawkins was beaten by Jules Radich, another right-leaning candidate, while former National party MP Nick Smith won in Nelson.

The day's brightest spot for progressives came from the capital, where Ms Whanau won a huge victory to become the first female Maori mayor.

Ms Whanau was the first runner in the race and upset favourite Paul Eagle - a local Labour MP who had Ms Ardern's support - who slumped to fourth.

Ms Ardern issued a statement on Saturday afternoon which did not address the Labour losses.

She instead congratulated successful candidates and pledged to work together "as we both face the long-term challenges of needing to grow our housing stock, keep investing in transport, public transport and our ageing water infrastructure".

Opposition leader Chris Luxon, whose National party did not endorse candidates, claimed the result reflected poorly on Labour reforms.

Under its Three Waters policy, Labour plans to strip local governments of their control of drinking water, wastewater and stormwater assets to improve their poor management.

Mr Luxon said victories to a number of candidates who opposed Three Waters - including Auckland's Mr Brown, Christchurch's Mr Mauger and Dunedin's Mr Radich - showed Kiwis did not support the reforms.

"With Labour tearing out the heart of local government with its Three Waters reforms, the role of local democracy has never been more important," he said.

"National will repeal Labour's Three Waters reforms and ensure water assets remain in local ownership."

In the deep south, New Zealand's longest-serving mayoralty was also ended after 24 years, with Sir Tim Shadbolt losing Invercargill.

Australian Associated Press