SYDNEY (AFP) - New Zealand Prime Minister Jacinda Ardern told Australia's leader to stop deporting "your people and your problems" to her country in a testy joint public appearance on Friday (Feb 28).

Ms Ardern tore into her counterpart Mr Scott Morrison over Australia's policy of forcibly deporting New Zealand citizens - even if they had lived almost all their lives in Australia.

"Look, I have been absolutely clear - this is corrosive to our relationship," Ms Ardern said bluntly as she described the problem as seen from Wellington during the joint press conference during her one-night visit to Australia.

"Australia is well within its rights to deport individuals who break your laws. New Zealand does the same. But we have a simple request - send back Kiwis," she said. "Genuine Kiwis."

"Do not deport your people and your problems," she said, complaining that some of the more than 2,000 people Australia has deported were de facto Australians.

The two leaders - from opposite sides of the Tasman Sea, the political spectrum, and the generational divide - had begun the press conference smiling in Sydney Harbour's sunshine, but the mood soon turned frosty.

Both looked on sternly as the other spoke, no doubt mindful of how the exchange will play with voters.

Ms Ardern faces a tough re-election battle later this year and Mr Morrison is reeling after a series of high-profile scandals and crises.

The 51-year-old Australian staunchly refused to change his government's policies - which are hugely popular with his conservative base - insisting anyone who "doesn't hold the title of 'citizen of Australia' does not get a special deal".

"Doesn't matter how long you have been here. It doesn't matter whether you turned up yesterday or many years ago," he said.

"If you are not a citizen of Australia, and you violate our laws, then under my government's policies, you will not be allowed to remain in Australia."

The pair also noted differences over climate change, with Ms Ardern referencing repeated Pacific Island calls for coal-producing Australia to do more to tackle growing emissions.

"We each know each other's policies," the 39-year-old said. "New Zealand's taken its position. Australia have taken theirs. And we discuss the expectations... that the Pacific rightly has of both of us."

Ms Ardern also offered her condolences to communities affected by the recent deadly bush fires, which experts say were made worse by climate-influenced drought and weather patterns.

"As we watched the smoke reach our shores, it only furthered our desire to do everything we could to support Australia," she said.