The prime minister, Malcolm Turnbull, has defended as “fair and just” and “moral” the policy of deporting New Zealanders who have committed crimes – even those who have never set foot in New Zealand or have Australian families.

Australia’s hardline policy of deporting non-citizens who have committed crimes that attract a jail sentence of one year or more has raised fierce political and public opposition in New Zealand, particularly around the deportation of people with no connection to that country.

Australia has forcibly deported 1,023 people to New Zealand in the last two years, and 44% of them have reoffended in that country, according to New Zealand’s police commissioner, Mike Bush.

The New Zealand prime minister, Jacinda Ardern, has consistently argued that Australia should deport only those with genuine links to New Zealand.

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Some of those who have been deported have had extensive criminal histories in Australia but no link to New Zealand beyond citizenship. Some have been issued with deportation orders despite having no family connections or friends in that country, or anywhere to go.

Alex Viane, 40, was born in American Samoa and became a New Zealand citizen as a child, but has never once entered the country, nor does he know anyone there. He has an Australian partner and children, and is being held in Villawood detention centre before an ordered deportation.

Jacob Symons, now in his 30s, left New Zealand as a one-year-old infant, but never gained Australian citizenship. He earned more than 200 criminal convictions in Australia and has been ordered for deportation. He has a brain injury and his abusive childhood was noted by the administrative appeals tribunal when it ordered his removal from Australia.

The issue of forcible deportations of New Zealand citizens was discussed by Turnbull and Ardern when they met in Sydney on Friday.

Turnbull said Australia’s policy would not change.

“The process is a fair and just one,” he said.

Asked specifically whether it was moral to deport people whose connections to Australia were far more significant than New Zealand, Turnbull said: “the answer to your question is yes”.

He said there was an appeals process open to those who were deported, and that 40% of the deportations appealed against had been successful so far. But he said the operation of the law would not change.

“It is our fundamental right and … we enforce our laws to assert our sovereignty and ensure that people were not Australian citizens, who commit serious offences, are deported. It does not just apply to New Zealanders. It applies to all non-citizens.”

Ardern told reporters she had raised the issue again with Turnbull, but that New Zealand was powerless to prevent the deportations.

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“I’ve raised again, as we have on previous occasions, elements of the deportation policy that have in particular been brought to our attention. We … are wanting to make the Australian government clear in our perspective … but it is in the hands of the Australian government to determine how they manage that element of policy.”

The two prime ministers discussed trade links, in particular the Trans-Pacific Partnership 11 (minus the United States), as well as co-operation in Iraq, and shared intelligence on cybersecurity.

New Zealand’s offer to resettle 150 refugees each year from Australia’s offshore processing regime remains on the table, but Turnbull again said Australia would not consider it until the US resettlement deal was completed.

The two leaders sought to emphasise the close relationship between the countries although significant policy differences remain.

For generations, New Zealand has been an outspoken campaigner for nuclear non-proliferation and disarmament. It has signed the UN’s nuclear weapons ban treaty enacted last year, and Ardern said her country would campaign for others to join the treaty to expedite its ratification into law.

The Australian government refuses to countenance the treaty, saying Australia relies on the extended deterrence of the US nuclear umbrella.

“In terms of the ... prohibition treaty, the weakness of it from our perspective is that the nuclear powers are not a party to it. We work internationally to prevent proliferation,” it has said.

“Everyone would like to aspire to a world which is free of nuclear weapons but we have to focus in the here and now, that is our perspective, in a very clear-eyed and pragmatic way in preventing proliferation, whether it’s the Korean peninsular or elsewhere. And in doing so, we have to work very closely with the existing nuclear powers including the United States.”

Both Australia and New Zealand are US allies, enjoined by the Anzus treaty and members of the Five Eyes security alliance. However, New Zealand does not assist with the US’s global nuclear regime (as Australia does) and has denied US ships carrying, or refusing to declare whether they are carrying, nuclear weapons access to NZ ports or waters.

“It will be of no surprise to any Australian and New Zealand has long taken a very firm stance on both nuclear proliferation and the existence of nuclear weapons generally,” Ardern said.

“It’s become part of our identity as a nation. Almost to the point of it probably doesn’t require restatement when we are on Australian shores. They understand our long-standing position in that regard.”