Kiwi international relations experts are aghast at the latest trans-Tasman war of words, which they say is proof of different values and a worsening relationship between Wellington and Canberra.
Australia's decision to strip citizenship from a dual Australian-New Zealand national currently detained in Turkey has created a new crack in the antipodean alliance.
Jacinda Ardern calls it an abrogation of responsibility.
Scott Morrison is unrepentant, saying he's simply acting in Australia's national interest.
Robert Ayson, professor of strategic studies at Victoria University in Wellington, says it shows "the cooperative part of the relationship with Australia is largely broken down".
"That's the angriest I've seen a New Zealand prime minister about an Australian counterpart. I haven't heard a New Zealand prime minister show their frustration about Australian counterparts in that way," he told AAP.
"This is something significant for the relationship."
Australia and New Zealand have had plenty to spat about in the past 12 months.
In February last year, Ardern lambasted Morrison at a joint press conference in Sydney over Australia's deportations policy, telling him: "Do not deport your people and your problems".
She used similar language in Wellington on Tuesday, saying: "New Zealand frankly is tired of having Australia export its problems".
In the year between, the two countries have rowed over trade, calling out China on human rights abuses and immigration practices - with many more terse words over deportations.
While Ardern was invited to participate in an Australian national cabinet meeting last May, the fact the two countries are yet to establish a trans-Tasman bubble also suggests an inability to get on the same page.
Robert Patman, professor of international relations at Otago University, said the disputes were not just over policy but showed a personal clash of perspectives between the two leaders.
"Jacinda Ardern has a different world view from Scott Morrison," he told AAP.
"Scott Morrison felt quite comfortable with Mr Trump, and the right of centre view of a world in which the great powers call the shots, the kiss-up, kick-down world. And I think Jacinda Ardern does believe passionately in an international rules-based system."
Professor Ayson said Tuesday's spat was a case of two leaders playing to their own constituencies.
"It's embedded in the domestic politics of both countries, which is going to make it hard to resolve it," he said.
"Jacinda Ardern was partly speaking to New Zealanders today, and a lot of New Zealanders would support the idea that Australia's not giving us a fair go on these issues.
"Similarly, it was clear Scott Morrison was speaking to his supporters with the national security angle. When it's in the domestic political context, it's harder to kind of deal with it as an issue."
Prof Ayson said the trans-Tasman relationship has always been "asymmetrical", with bigger brother Australia often pulling rank.
"New Zealand needs Australia more than Australia needs us," he said.
There's a strong sentiment in New Zealand of having been wronged by Australia, time and again.
As has been noted by many a Kiwi observer in the past 24 hours, New Zealand's treatment of Christchurch mosques terrorist Brenton Tarrant shows the disparity in values.
The Australian was raised and radicalised at home, moving only to New Zealand in the months before his atrocity.
Still, New Zealand accepted the need to show him justice through a dignified sentencing process, and is now housing him as he serves life in jail.
That has already cost New Zealand tens of millions of dollars, on top of the 51 lives and countless other shattered families and communities.
Professor Patman said rows were likely to continue if an "emboldened" Ardern saw them as worthwhile.
"In the space of three years, Jacinda Ardern had more unprecedented problems thrown at her than many other leaders in the entire lifetime," he said.
"And she had a landslide (election) victory. She has a global profile. I don't think it's gone to her head, I think she's just become more blunt-speaking than she might have been if her domestic position was weaker.
"She may have made an assessment with Scott Morrison based on her discussions with him, that she has to be very frank."
Ayson said further brouhahas could hurt New Zealand's ability to meet international goals.
"If both New Zealanders and Australians start to see the relationship through prisms of disagreement, it's going to complicate it," he said.
"This is not the sort of thing that is going to make it easier when New Zealand and Australia want to put their relationship into the next gear, and movement of people is part of that."