It's the sign of a mature relationship that New Zealand's High Commissioner to Canberra has no qualms recommending Kiwis become Australian citizens.

And increasingly, they are doing so: either translating long residencies in Australia to becoming citizens, or taking that leap to move from New Zealand in search of economic opportunity.

New Zealand has almost always bled citizens to Australia, a core function of the asymmetric relationship between the allies.

The opportunity was formalised in 1973 with the Trans-Tasman Travel Arrangement allowing citizens to visit, live and work on both sides of the ditch.

However, a 2001 change made many Kiwi migrants ineligible for citizenship in Australia, essentially blocking access to welfare, study loans, the chance to vote, and work in various public fields.

In 2023, to coincide with Anzac Day commemorations, Anthony Albanese's government cleared the way again, allowing Kiwis access to an Australian passport after four years of residency and a smaller fee.

AAP can report that 36,721 Kiwis have acquired Australian citizenship in the 15 months since.

Andrew Needs, New Zealand's top diplomat in Australia, wants more to follow.

"There's tens of thousands taking that up, but there's a lot more that could," Needs told AAP.

"Some don't fully realise that their rights are not complete without citizenship.

"Talking to Kiwis that have been here a while and are eligible for that pathway to citizenship, some of them say, 'Oh no, I'm a loyal Kiwi'.

"And I say 'well you can still be a loyal Kiwi, and you can have dual citizenship, and all the benefits ... you can still barrack for the All Blacks, for Lisa Carrington at the Olympics.

"It's not my job to get out and tell people to take Australian citizenship, but that pathway is there and I really think it's a thing Kiwis should be thinking about."

Needs certainly isn't advocating Kiwis depart New Zealand, the country he has represented as a career diplomat for 36 years.

He is merely echoing the country's position both before and after Australia changed its citizenship pathway — that Kiwis deserved a better deal in Australia.

"Everything tells you that New Zealanders make great migrants to Australia," he said.

"Workforce participation rates are higher — 71% compared to 61 for the national average — and they earn about 18% more. We're great, great migrants."

New Zealand is currently experiencing never-before-seen levels of outward migration.

In the year to August, Stats NZ reports a record 134,000 people migrated from New Zealand. In the year before, 115,000 did so, meaning a quarter of a million, or almost 5% of the population have left in the past two years.

The ABS holds data on the number of NZ citizens moving to Australia, which is running at the highest level in over a decade.

In the year to March, around 47,000 made the move, for a net loss of almost 30,000.

This is largely viewed a function of New Zealand's post-pandemic economic malaise, in and out of recession for two years.

However, privately, some New Zealand leaders hold concerns Australia's open door is exacerbating the brain drain.

New Zealand is not experiencing population decline as it is letting in an even bigger number of migrants, primarily to ease skills shortages experienced through the pandemic.

Given the need for workers, the in-flow is not seen as politically controversial.

The huge out-flow is associated with political and economic failure, fuelling a debate as to who should take ownership of loss of Kiwi talent.

"It's a reflection of the situation the country was left in after six years of a Labour government," Finance Minister Nicola Willis said.

"We had an economy that had a dire cost-of-living crisis, inflation out of control, interest rates had skyrocketed, and that has had a punishing effect on the economy."

Opposition leader Chris Hipkins says emigration is a "vote of no confidence in the current Government".

"In the building and construction sector we are seeing an exodus of talent, there 10,000 fewer jobs in that sector now than ... just one year ago," he said.

"A lot of those people are highly-skilled people who are in demand around the world so they've jumped on a plane and they've got other work."

Many industries and key professions are losing workers across the Tasman.

Earlier this month, Sky News reported that 141 Kiwi police had transferred to Australia since the start of 2023.

Anecdotally, there have been increases in doctors, nurses, engineers, corrections staff and defence personnel lured across.

From July, Kiwis can enlist in Australia's armed forces for the first time: provided they have lived in Australia for a year and haven't been in the New Zealand Defence Force for two years.

Graeme Muller, NZ Tech chief executive, said his industry was engaged in the "constant challenge of maintaining a competitive employment environment for New Zealand tech companies".

Last year, the game development sub-sector experienced a short-term brain drain owing to an Australian initiative giving a 20% subsidy for development costs.

"This enabled them to increase staff pay and attract talent ... the NZ government responded quickly to this introducing a rebate in 2024 which countered the potential brain drain and returned the NZ game sector's competitive balance," he told AAP.

Teachers are also moving in numbers.

The NZ Teaching Council can crudely understand movement based on registration checks conducted on New Zealand-registered teachers.

In 2019, 589 checks were conducted, and in both 2023 and 2024, that number has roughly doubled to be equivalent of one per cent of the Kiwi workforce in each year.

The migration story is just one part of why Needs calls New Zealand's relationship with Australia "the most complete and complex relationship we've got".

By Ben McKay of AAP