New Zealand will resettle 150 refugees stuck in Australia's offshore detention system per year for three years, finalising a deal first made nine years ago.

The deal was first struck by former prime ministers Julia Gillard and John Key in 2013 and would see 150 asylum seekers a year resettled across the ditch.

The Coalition had been hesitant to follow through with the agreement because it was concerned it could see refugees, who go to New Zealand, try and travel back to Australia and settle permanently here.

But the government has backed down from that concern, as there is nothing in the deal that would prevent the refugees from attaining permanent residency or citizenship and returning to Australia.

The deal will only apply to refugees already in detention and not to future asylum seekers who arrive by boat.

Loading

Home Affairs Minister Karen Andrews said the government's offshore detention policy remained unchanged.

"This arrangement does not apply to anyone who attempts an illegal maritime journey to Australia in the future," Ms Andrews said. 

"Australia remains firm – illegal maritime arrivals will not settle here permanently. Anyone who attempts to breach our borders will be turned back or sent to Nauru."

New Zealand Immigration Minister Kris Faafoi said the country's offer to take refugees reflected its humanitarian spirit. 

"New Zealand has a long and proud history of refugee resettlement and this arrangement is another example of how we are fulfilling our humanitarian international commitment," Mr Faafoi said. 

"We are pleased to be able to provide resettlement outcomes for refugees who would otherwise have continued to face uncertain futures."

Shadow Home Affairs Minister Kristina Keneally said she didn't trust the federal government to actually implement the deal.

"This is a humiliating backflip for Scott Morrison who claimed as recently as 2018 that New Zealand’s generous offer to resettle refugees would see people smugglers restart their evil trade," Senator Keneally said.

Ms Andrews said Senator Keneally's comments that the government might not deliver the deal "couldn't be further from the truth".

"This is a great day, we all have worked very hard to facilitate this arrangement."

UN high commissioner says hundreds still left stranded after deal

Refugees who apply to resettle in New Zealand will need to have been referred by the United Nations High Commissioner for Refugees (UNHCR), and will be required to go through the country's screening process, which tests their credibility, security threat, and conducts health assessments.

In a statement, UN high commissioner representative Adrian Edwards said the UNHCR had long advocated for Australia to accept the New Zealand offer.

"For the refugees and asylum seekers, the prolonged uncertainty of their situation has taken an enormous toll," Mr Edwards said.

"We nonetheless hope it will bring about new impetus towards this goal so that compassionate and lasting answers can be found, including in Australia for all who have been subject to Australia’s offshore processing policies."

Greens senator Nick McKim wrote on Twitter the announcement was a "blessed, belated relief".

"But we cannot forget the lives that were needlessly destroyed by the arbitrary brutality of offshore detention," he wrote.