Australia’s increasing nuclearisation will not change New Zealand’s longstanding ban on nuclear-propelled vessels entering New Zealand’s waters, according to both Labour and National.

The New Zealand Government has also reminded Australia of a 1980s treaty the country signed that established a nuclear weapons-free zone in the South Pacific.

Under the Aukus agreement between the US, Australia, and the UK, Australia will take delivery of at least three, potentially second-hand, Virginia-class submarines early next decade - although this would need to be approved by the US Congress.

Australia would also have the option to purchase a further two submarines.

But nuclear submarines are likely to be seen in Australia much sooner, with British nuclear submarines rotating to Australia from as early as 2027 to build up the knowledge and workforce necessary for the delivery of Australia’s submarines.

All of the submarines delivered under the deal will be nuclear-powered, but not nuclear-armed.

Prime Minister Chris Hipkins said New Zealand “continues to be a proudly nuclear-free state. Our position on that is not going to change”.

“We are not part of the [Aukus] arrangement around the nuclear submarines, and are not going to be part of that arrangement, but the UK, the US and Australia are incredibly important partners for us including in the defence area.”

The 1987 legislation establishing the nuclear-free zone expressly prohibits any ship “whose propulsion is wholly or partly dependent on nuclear power” from entering New Zealand’s territorial waters.

Relaxing that for Australia’s nuclear submarines would require a law change, which neither Labour, nor National wish to do.

Deputy National leader Nicola Willis, stepping in for Christopher Luxon who is isolating with Covid-19, said National would not be changing New Zealand’s nuclear-free policy.

“We stand for a nuclear-free New Zealand,” Willis said.

Luxon previously confirmed to the Herald that he supported the nuclear free policy and would not change it.

“What we are seeing around the world is the geopolitical environment is less stable than it once was and we are seeing that our defence friends and partners around the world are increasing their investment in defence,” Willis said.

“I think it’s important that New Zealand continue to be good friends to people like Australia so that if we ever have a time of need, we can call on them.”

Foreign Minister Nanaia Mahuta said the Government had been briefed on the announcement ahead of time by Australia. Australian media have reported several calls were made by Australia to friends and allies ahead of the announcement.

When asked about New Zealand joining the Aukus agreement in some non-nuclear capacity, perhaps relating to the development of artificial intelligence or cybersecurity tools, Mahuta appeared open-minded, but cited the Treaty of Rarotonga - a 1985 agreement establishing a nuclear weapons-free zone in the South Pacific and banning the use, testing, and possession of nuclear weapons within the zone.

Australia also signed the agreement.

“New Zealand has been really clear that in relation to those arrangements that the Treaty of Rarotonga is something that is very important to us in terms of the views of the Pacific,” Mahuta said.

“We assert our interests based on our independent foreign policy and what is good for the Pacific region.

“We have kept open future discussion around issues such as cybersecurity.”

As well as being Foreign Affairs Minister, Mahuta is also the Minister for Nuclear Disarmament.

Mahuta said that when New Zealand was briefed on the arrangement, the Government reminded Australia of the Pacific nuclear weapons-free zone.

“We made very clear that the Treaty of Rarotonga is an important consideration for our region.

“We have asserted that we want the Treaty of Rarotonga upheld because it is important for the Pacific and that assurance has been given by Australia.”

Some in Australia are currently discussing whether American nuclear weapons have a place in Australia, potentially as part of a defensive hedge against China.

Australia’s international treaty arrangements prohibit Australia from permanently housing nuclear weapons on its soil, but Australia’s most senior defence public servant indicated last month that American planes rotating through Australia could carry nuclear warheads without breaching the treaty.

The Sydney Morning Herald reported that the public would never be informed whether such aircraft are carrying nuclear weapons under the US’s policy of neither confirming nor denying the presence of nuclear warheads on its vessels.

Department of Defence Secretary Greg Moriarty told Senate estimates hearings that the “stationing of nuclear weapons in Australia is prohibited by the South Pacific Nuclear-free Zone Treaty to which Australia is fully committed”.

But he also said there was “no impediment under this treaty or the Nuclear Non-proliferation Treaty to the visit of foreign aircraft to Australian airfields or transit of Australia’s airspace, including in the context of our training and exercise programs and Australia’s force posture co-operation program with the United States.”

The US is preparing to build dedicated facilities for up to six B-52 bombers at Tindal air base, south of Darwin. Those bombers can carry nuclear weapons.