Prime Minister Jacinda Ardern should "proceed with caution" when criticising Australia's handling of refugees on Manus Island, says National's foreign affairs spokesman Gerry Brownlee.
Ms Ardern blasted Australia's handling of the issue as unacceptable as she sought another meeting with Australian Prime Minister Malcolm Turnbull.
Ms Ardern has continued to push New Zealand's offer to accept 150 refugees and asylum seekers from Australia's offshore detention centres since her first face-to-face meeting with her Australian counterpart in Sydney a week ago.
She wants a more substantive conversation at the East Asia Summit this week.
Mr Brownlee told NZ Newswire on Sunday it was "surprising she's decided to go so hard on the Australians".
"All I would say is recognise there is a whole lot of things at play here, not the least of which is these were people trying to enter Australia illegally."
He said Australia did accept refugees.
"What I do know is that one of the concerns the Australians will have is if these people come to New Zealand and they get residence here and then of course because New Zealanders have pretty much free access into Australia they have backdoor way into Australia."
Mr Brownlee said Australia had a problem with having a huge sea border close to a part of the world people were trying to escape from.
"I've said proceed with caution," he said.
He said the previous National-led Government in New Zealand had made the offer to take 150 refugees and had respected Australia's decision.
Ms Ardern said her Government made the offer to accept 150 refugees "because we saw a great need".
"No matter what label you put on it there is absolute need and there is harm being done," she said early on Sunday morning while in Vietnam for the APEC summit.
"I see the human face of this and I see the need and the role New Zealand needs to play. I think it's clear that we don't see what's happening there as acceptable, that's why the offer's there."
It was her strongest statement to date against the unfolding crisis.
Four hundred refugees and asylum seekers have barricaded themselves inside the mothballed detention centre, fearing for their safety if they leave.
The United Nations has raised concerns over reported instances of assault, sexual abuse, self harm and suspicious deaths.
Ms Ardern hasn't revealed the content of the talks with Mr Turnbull, but said the fact they are continuing proved the urgency of the situation.
New Zealand won't pursue a deal directly with Papua New Guinea, despite Foreign Minister Winston Peters spotted holding talks with PNG's Prime Minister Peter O'Neill.
Ms Ardern said it was faster to organise the logistics of any deal with Australia.
"It continues to be the easiest option is to go through Australia given the screening that's already occurred of those refugees... I'm interested in the fastest route," she said.
Mr Peters has made it clear New Zealand's offer also includes refugees and asylum seekers in Australian detention centres in Nauru.