New Zealand better off outside AUKUS: Clark

Key Kiwi foreign policy thinkers believe being left out of AUKUS will bring strategic advantages for New Zealand, including an improved relationship with China.

The huge defence agreement Australia has signed with the United Kingdom and the United States could also see New Zealand pressured to ratchet up spending on its own maritime defence.

The fall-out from Australia's deal to acquire nuclear submarines is being keenly assessed across the Tasman in New Zealand, which counts Australia as its only military ally.

Being a part of AUKUS was a non-starter for Wellington given its long-standing non-nuclear stance.

Former Prime Minister Helen Clark has voiced her opposition to the deal, questioning the need to align so explicitly with American defence policy.

"New Zealand interests do not lie in being associated with AUKUS," she posted on Twitter.

"Association would be damaging to independent foreign policy."

New Zealand prides itself on its independent foreign policy and its nuclear-free policy, as reiterated by Foreign Minister Nanaia Mahuta, who is visiting China this week.

"That won't change. New Zealanders don't want to see that change," Ms Mahuta said.

New Zealand's diplomatic dividend could extend into the Pacific, with Ms Mahuta stressing its "Pacific-led approach" to regional issues.

Ms Clark agreed with former Pacific Islands Forum secretary general Meg Taylor, who argues Pacific nations were not consulted but instead sidelined by AUKUS.

New Zealand's opposition has raised concerns with the deal.

National party foreign affairs spokesman Gerry Brownlee told AAP that AUKUS makes New Zealand less safe by painting "China as the enemy" and gives allied trans-Tasman defence forces inter-operability concerns.

University of Otago professor Robert Patman said New Zealand stood to benefit from its more nuanced relationship both with China and other nations skeptical of AUKUS.

"China is too big to be contained. AUKUS gives China a bit of a propaganda windfall," he told AAP.

"It enables them to reiterate their familiar narrative about the Cold War mentality of the United States and Australia and the UK.

"I don't think New Zealand strategically would benefit by being inside the organisation.

"One of the great diplomatic assets New Zealand's had over the years has been able to present itself as a country that's not afraid of making independent decisions."

Dr Patman said being outside AUKUS would allow New Zealand to diversify its trade more easily with south-east Asian nations that did not like the tie-up.

Winston Peters, the grand veteran of New Zealand diplomacy and foreign minister under Ms Clark and Ms Ardern, said there was a danger in over-analysing the AUKUS agreement.

"It just means that Australia intends to have better defence utility," he told AAP.

Mr Peters laughed off Paul Keating's opposition to deal, saying Australia needed more military heft and the former PM was "talking bulldust".

The 77-year-old said AUKUS showed the need for increased military investment in New Zealand, attacking Mr Brownlee's argument that New Zealand was made less safe by AUKUS.

"That is an astonishing statement to make," he said.

"The reality is, as proven to be so true in so many cases in history, the best deterrence from attacks is the threat that the attack is going to be a failure."

Dr Patman agreed with the need for New Zealand to follow Australia in growing its naval strength.

"New Zealand has the fourth or fifth largest exclusive economic zone in the world to defend and it seems to me that we need a lot more investment in maritime capabilities," he said.

"There's going to be an increasing number of countries competing for resources in the future, and that very large economic exclusive zone might look quite tempting."