The Prime Minister has accused National of peddling a "factually incorrect" narrative about a global migration promise New Zealand signed up to last year.
Jacinda Ardern said the United Nations Global Migration Compact - signed by the Government in December - "wouldn't have the effect the National Party claimed".
"I did hold concerns because we weren't having a debate that was anchored in the facts," the Prime Minister said at her Monday post-Cabinet press conference.
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"They claimed that we wouldn't hold sovereignty over our own borders - that was totally, factually incorrect and remains incorrect."
The Prime Minister's comments followed Deputy Prime Minister Winston Peters' call on Sunday for Simon Bridges to resign over promising to withdraw New Zealand's support for the UN pact, if National's elected in 2020.
The international agreement's aim is to coordinate migration policy worldwide, but it's non-binding and has no effect in law. But National opposed it, claiming New Zealand could lose the ability to determine its own migration policy.
Peters told Newshub far-right groups now believe the UN pact is binding, and suggested the National Party provoked anti-immigrant rhetoric by promising to withdraw New Zealand from it.
But Bridges maintains that National is not anti-immigration, telling Magic Talk on Monday he simply wants New Zealand to decide its own migration laws, not the United Nations.
"What you've got with the Government under Jacinda Ardern and Winston Peters is they seem to want to impress the UN more than they want to impress New Zealanders."
He highlighted how National wasn't alone in its rejection of the pact, pointing to the governments of New Zealand allies Australia and the United States who haven't signed up.
Peters revealed on Sunday he received death threats from far-right extremist Philip Arps - the man jailed for sharing the Christchurch shooting video online - after he signed New Zealand up to the UN pact.
Ardern said opposition to the pact came from a "very particular group who had a very particular desire, and you can see by those who jumped on the bandwagon what they were trying to do".
She said she would "never sign away the sovereignty and maintenance of our own immigration policy", adding that she sees it as a "core, fundamental role we have as a Government".
When asked if she had received similar threats to Peters, Ardern said: "Those are an operational matter that really sit with police and that's where I am quite happy to leave it."
The Prime Minister received death threats on social media earlier this year following the March 15 Christchurch mosque shootings by a suspected white supremacist.