Prime Minister Jacinda Ardern says Australia's deportation policy "is not right" and she will speak frankly with her Aussie counterpart, Scott Morrison, about the issue during a one-night trip to Sydney later this week.
"We are friends but friends need to speak frankly with one-another," she told TVNZ1's Breakfast this morning.
"It is fair to say that when we've had disasters - coronavirus, White Island, their bushfires - you see the closeness of our relationship then, but that is not going to stop me raising issues like citizenship and deportation which do continue to be corrosive."
Ms Ardern told Breakfast Australia's deportation policy concerning convicted Kiwis is "having a social impact on New Zealand, it is impacting on gangs in New Zealand and it is impacting on our relationship".
Ms Ardern arrives in Australia on Friday for the annual leaders meeting between the trans-Tasman allies.
"The Australian government is well within rights to take the policy on citizenship and deportation that they have. They are within their rights to do that - that doesn't mean that it's the right thing to do.
"It is having a social impact on New Zealand and it is having an impact on New Zealanders who have chosen to call Australia home and are taxpayers and contributing members their society when their kids can't get the kind of, for instance, disability support that an Australian could get in New Zealand.
"I'm not willing to go into a race to the bottom and play tit for tat politics. That's not how New Zealanders do things. But I am willing to keep advocating on behalf of New Zealand and say the deportation policy as it stands is not right."
Ms Ardern said she doesn't have "some magic answer" given Australia isn't acting outside the law.
"They can do it - most New Zealanders don't believe they should," she said.
This morning, opposition leader Simon Bridges said in a statement a National Government would look at amending the law to allow Australians convicted of serious crimes in New Zealand to be deported.
If elected, National will explore a policy based on amendments to Australia’s Migration Act in 2014 which allows for people to have their visas cancelled on character grounds.
"It's the legal right of the Australian Government to deport Kiwi criminals. However, we have the same rights and it's my view that New Zealand needs to explore how a reciprocal policy could work here.
"While Jacinda Ardern has labelled this issue as corrosive to our relationship with Australia, I don't agree. In principle, if it's right for Australia, it's worth exploring whether it's also the right position for New Zealand and our interests."
Before reaching Australia, Ms Ardern will spend three days in Fiji on her first state visit to the Pacific nation.
Fijian Prime Minister Frank Bainimarama and Ms Ardern will discuss further collaboration on climate policy, but the issue won't be on the agenda in Sydney.