Former New Zealand prime minister Jacinda Ardern “berated” Scott Morrison in heated disagreements between the pair on migration issues, it has emerged.

New Zealand’s High Commissioner to Australia, Annette King has revealed the depth of feeling behind some trans-Tasman stoushes during her five-year term.

Dame Annette, who retires at the end of the year, said there were heated rows behind closed doors, and Ms Ardern at one point became “really angry” with Mr Morrison.

Australia’s migration policy – under which New Zealand-born criminals were deported, even if they had lived all their lives on this side of the Tasman – was particularly contentious.

The issue plunged relations to a low in 2020, when Ms Ardern (now also a dame) confronted Mr Morrison at a joint press conference, telling him “do not deport your people and your problems”.

“It certainly upset the Morrison government … the previous government was angry with her for raising it [even though] she had already warned that she would,” Dame Annette said.

“She berated ScoMo on his treatment of New Zealanders. It was a really important signal back home to New Zealand.”

“[But] there was no way there was going to be any change under the previous government.”

Dame Annette said the Morrison’s government decision to remove the citizenship of a dual Australian-NZ national living in Syria under Islamic State was a real flashpoint.

Australia’s move, which Ms Ardern angrily labelled an “abrogation of responsibility”, left New Zealand solely responsible for the woman, who had been detained on the Syria-Turkey border with two young children.

“[She] was brilliant on that issue because it was a surprise to us. The way it was presented to her, it left her really angry,” she said.

“Friends don’t do that to each other. I don’t think you’ll ever see that happen again.”

Dame Annette finishes her five-year term with Australia-New Zealand relations on a high, buoyed by Prime Minister Anthony Albanese’s offer of citizenship to Kiwi residents.

Jacinda Ardern and Anthony Albanese in Sydney just after the 2022 election.

From Saturday, hundreds of thousands of New Zealanders living in Australia become eligible for citizenship, ending a two-decade dispute over the treatment of Kiwis.

Dame Annette said New Zealand was surprised and grateful for Australia’s decision.

“For years and years, New Zealand has complained about the way New Zealanders have been treated in Australia,” she said.

“We got more than we hoped for in that announcement.”

The changes, announced on Anzac Day, allow Kiwis who have spent four years in Australia to gain citizenship.

Citizenship brings important benefits, including access to welfare, student loans, disability support, public housing, work in the federal public service or armed forces, and voting rights.

New Zealand officials were confident they would see a policy change from Labor after it won the 2022 federal election. Ms Ardern’s hastily organised trip across the ditch in the days after sealed the deal.

“Just after Albanese became the Prime Minister, she came straight over and had dinner with him at Kirribilli House,” Dame Annette said.

“He reaffirmed to her what he was going to do. He was incredibly enamoured with her advocacy.”

New Zealand has won other concessions from the Albanese government, including a reduction in the number of criminal deportees shipped across the Tasman.

Mr Morrison, meanwhile, disputes there was pushback against Ms Ardern on the issue.

A spokesperson for the former PM said he enjoyed a “positive, productive and professional relationship with Ms Ardern” and while he didn’t change the policy, he worked to manage the disagreement “sensitively”.

Elsewhere, Dame Annette said the Australian changes on deportations and citizenship left her with the impression that New Zealand should stand up to its only formal ally more often.

“New Zealanders are known to be polite. And Australians are seen to be straightforward. You’re never left in doubt what Australia thinks,” she said.

“We could take a leaf out of Australia’s book actually and be polite with purpose.

“If Australia is thinking something, at an officials level or a political level, they will tell you, where we will listen politely.

“But you saw from Jacinda Ardern’s response to the deportations, the 501s, and to the stripping of citizenship, a public rebuke of Australia that you would not have seen often in the past.”

– with AAP