Labour Foreign Affairs spokesperson David Parker is calling for the Government to join an international lawsuit alleging Israel is committing genocide against Palestinians in its war against Hamas.
In a statement on Wednesday, Parker also called for the "carnage" in Gaza to end.
He claimed much of the Israeli public was "distressed" by genocide allegations, which was brought against the country by South Africa in the International Court of Justice late last year.
Since the Israel-Hamas war broke out three months ago, Gaza health authorities have said more than 23,000 have been killed - many of whom were civilians.
The bombardment was in response to an October 7 rampage by Hamas fighters who Israel said killed more than 1200 people and kidnapped 240.
New Zealand responded last month by joining Australia and Canada in calling for another pause in the fighting. Aotearoa was also among 153 UN members to vote for an immediate humanitarian ceasefire in December.
But Parker said Israel had "shown no intention of letting up".
"South Africa has taken allegations of genocide in Gaza to the International Court of Justice, a claim which Israel denies.
"The International Court of Justice is the appropriate body to investigate and determine whether the Genocide Convention has been breached and whether the international laws relating to war are being breached.
"New Zealand under the former Labour Government 'intervened' in the recent genocide case between Russia and Ukraine at the International Court of Justice and made legal submissions to support the Court in its deliberations. New Zealand should do the same now for Gaza.
"The New Zealand Labour Party is calling on the Government to participate in the legal action being led by South Africa regarding Israel's acts of war in Gaza," the statement said.
Newshub has contacted duty minister Erica Stanford for a response.
Israel, meanwhile, has called the lawsuit "atrocious and preposterous".
"Our enemies, Hamas, in their charter, call for the destruction of our nation, the state of Israel - the only nation-state of the Jewish people," Israeli President Isaac Herzog said on Tuesday.
"We will be there at the International Court of Justice and will present proudly our case of using self-defence under our most inherent right under international humanitarian law."
The case was set down to begin later this week.
