New Zealand recorded a net gain of Australian migrants in the year to January 31 - the continuation of a trend which could be due the relative strength of the two economies, says ASB economist Daniel Snowden.

The big migration trend, which has underpinned New Zealand's strong economic growth, shows no sign of letting up.

Numbers released today for the year to January 31 showed an overall net migration gain of 71,300.

That's a record for a 12-month period and the first time in New Zealand's history the gain has topped 71,000.


However ASB's Snowden notes: "Returning Kiwis were not the main driver this month, with a net 385 NZ citizens actually leaving the country."

"This is in contrast to recent months, where returning New Zealanders were a key driver of rising net migration. However, the slack was taken up by Australian citizens, with a net 633 people choosing NZ over Australia."

While the numbers are relatively small, they buck the historic pattern which has seen large numbers New Zealanders migrating to Australia for years.

At the height of the mining boom in 2012 New Zealand's net loss to Australia was 39,800 residents.

But in the year ended June 2016, that had shifted to a net gain from Australia of 1,900.

The latest figures showed a continuation of that trend, Snowden said.

"It could be New Zealand's realtively strong labour market," he said.

New Zealand had employment growing at a record rate while Australia had a poor economic performance in third quarter of the year.

Immigration looks set to be a key election issue with the opposition parties having highlighted the affect new arrivals may be having on house prices and other key infrastructure areas such as roads and schools.

The Government, along with many economists, argue strong immigration flows are a measure of the country's success and contribute positively to the wider economy.

New Zealand's economy is growing at 3 per cent and a year and is expected to accelerate.

However, on a per capita basis (accounting for the big population gain) growth is more like 1 per cent.

A New Zealand Initiative report released last month concluded that "economic worries about immigration are overblown".

It argued that migrants' influence on house prices and unemployment are marginal while the value they add to the Government accounts is, on average, greater than that of citizens.

However, the report did note that a rapid population gain was putting the squeeze on infrastructures, such as roads and schools, and was creating short-term costs.

Immigration looked set to be a key issue for election year, said Westpac senior economist Satish Ranchhod.

The public concern about housing costs wasn't abating, he said, and the Government plan to resolve the issue by building additional houses could take a long time to work.

"We do think that migration could be one option that's mooted. Particularly as part of post-election coalition discussions."

"We expect net migration inflows to remain strong for some time, with NZ's positive economic story, including its labour market, making us a very attractive destination," Ranchhod said.