The Green Party says it opposes the US-led strike on Syria, taking a harder line than the Prime Minister.
The US, France and the UK hit the Middle Eastern nation on Saturday (NZ time) in retaliation for a suspected chemical weapons attack earlier this month.
Jacinda Ardern said on Saturday New Zealand "accepts why" the strikes, which targeted Syrian chemical weapons facilities, took place.
"The action was intended to prevent further such atrocities being committed against Syrian civilians.
"We stand firm in our condemnation of the use of chemical weapons in Eastern Ghouta. This is clearly in breach of international law."
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But the Greens, who are not part of the formal coalition but do hold ministerial positions, say they're opposed to the "Trump-led" strikes.
"Bombing and violence in the Middle East has never led to peace," the party said on Twitter on Sunday.
"The current conflict is a power play between the US and Russia with innocent civilians literally trapped in the middle."
In an article for The Spinoff, Green MP and former refugee Golriz Ghahraman said the US, France and UK themselves have breached international law.
"Those bombs will kill and maim more people; they will bring more violence and irrevocable suffering to an already traumatised people. No one has ever in fact bombed for peace. We know that so why do it again?"
While she criticised Russia's repeated use of the veto at the UN Security Council, preventing the world from taking action as a unified force, her strongest condemnation was for US President Donald Trump, who ordered the attacks without first getting approval from his own government.
"It was very telling that in Trump's statement on air strikes he did not claim the attack was consistent with the UN Charter or was a legal response to the use of chemical weapons. He simply said that the attacks were in the national security of the United States. What he should have said was the attack served US economic interests," wrote Ms Ghahraman.
"This war would not have been as bloody or long lived had it not been for the eager involvement of the US, Russia and their allies, and for their unwillingness to pressure their regional allies to divest from the cheap oil coming from either Iran or Saudi."
Ms Ardern said the issue now needed to go back to the UN Security Council. New Zealand in recent years has called for an end to the veto wielded by the five permanent members of the Security Council - the US, France, UK, China and Russia.
Ms Ghahraman's family fled Iran when she was nine.