Australia's tough immigration policies are increasingly straining relations with New Zealand, as the deportation of long-term Australian residents to New Zealand becomes an election issue there.

Key points: Australia has deported more than 1,600 people to NZ in the past five years

Australia has deported more than 1,600 people to NZ in the past five years Jacinda Ardern says the policy is having a "social impact" on NZ

Jacinda Ardern says the policy is having a "social impact" on NZ NZ's Opposition will "explore" deporting Australian criminals

New Zealand's Prime Minister Jacinda Ardern has vowed to once again raise the policy she "fiercely disagrees with" when she meets Prime Minister Scott Morrison in Sydney today.

Meanwhile, Opposition Leader Simon Bridges has raised the stakes by threatening to reciprocate by deporting criminals to Australia if he comes to power.

"Australia is within their rights to do what they are doing, it doesn't mean what they are doing is right," Ms Ardern said earlier this week.

In the last five years, Australia has deported more than 1,600 people to New Zealand under provisions in the Migration Act that allow the government to remove foreigners who are not of good character or pose a threat to the safety of Australians.

Many are convicted criminals who were born in New Zealand but have lived most of their lives in Australia and have no connections in their country of origin.

The New Zealand police association has linked the deportees with a rise in gang activity across the country.

"It is having a social impact on New Zealand, it is having an impact on gangs in New Zealand and it is impacting our relationship (with Australia)," Ms Ardern said earlier this week.

The Morrison Government has no intention of backing down on the practice, having consistently emphasised its priority on ensuring the safety of Australians.

Could New Zealand give Australia a taste of its own medicine?

Simon Bridges, leader of the Opposition National Party, has vowed to "explore" reciprocating by deporting criminal Australians who have been residing in New Zealand.

New Zealand voters are set to go to the polls on September 19 and opinion polling currently has a centre-right coalition led by the Nationals neck-and-neck with Ardern's Labour-led coalition.

"Enough is enough, the reality is they've been doing it to us for some time, and fair is fair," Mr Bridges said.

The call to reciprocate is proving popular with voters in New Zealand, but Ms Ardern has dismissed the idea as "naive."

There are more than 650,000 New Zealanders living in Australia, but only around 62,000 Australians living in New Zealand.

It means ten times as many New Zealand citizens would be affected if immigration policies between the two countries were caught up in tit-for-tat measures.

"It's a matter of principle and it's a matter of proportion," said Ms Ardern, confirming she would not pursue reciprocal deportations.

Coronavirus and Indigenous affairs on the agenda, but not climate change

Ms Ardern will meet both Governor-General David Hurley and New South Wales Premier Gladys Berejiklian before a formal bilateral meeting with Mr Morrison at Admiralty House, the Governor-General's residence.

The two leaders will discuss a co-ordinated response to the coronavirus outbreak, as well as regional security, trade and co-operation in the Pacific.

Australia and New Zealand will also set out a plan to work more closely on Indigenous issues.

Minister for Indigenous Australians Ken Wyatt and Minister of Maori Development Nanaia Mahuta will join the leaders at Admiralty House to sign an Indigenous Collaboration Agreement.

Ms Ardern has arrived in Sydney following a visit to Fiji, where she was praised for her "sincere empathy for our suffering through a changing climate" by Prime Minister Frank Bainimarama.

But despite the desire of many Pacific countries for New Zealand to join their efforts to pressure Australia to adopt stronger emissions reduction targets, she will not be raising the issue with Mr Morrison today.

"This idea that somehow me going in and wagging my finger is going to change another country's domestic policy, I don't think is an accurate representation of the way any of us do politics," she said.

"I make New Zealand's view very clearly known and I do that at forums like the Pacific Islands Forum."

ABC