Jacinda Ardern will support legislation to lower the voting age to 16 after New Zealand's top court ruled denying 16 and 17-year-olds the vote was inconsistent with the country's bill of rights.
On Monday, the Supreme Court found the current voting age of 18 unfairly discriminated against younger Kiwis after a three-year campaign from activist group Make It 16.
Make It 16 had pursued a court ruling given the bill of rights offers legal protection from discrimination on the basis of age for New Zealanders aged 16 and over unless there are reasonable justifications.
"This is history," Make It 16 co-director Caeden Tipler told journalists outside the court in Wellington.
"We are very optimistic that once parliament reviews the decision they will see that lowering the voting age is the right thing to do."
The government reacted swiftly to the ruling, announcing hours later on Monday afternoon that cabinet had considered it and would draft a bill to lower the minimum voting age to 16.
The law should be introduced early next year and if successful, would take effect after the 2023 poll.
"This is an issue best placed for parliament for everyone to have their say ... I personally support a decrease in the voting age," Ms Ardern said.
"For me, it's alignment around some of the responsibilities and rights that are already apportioned at these different ages but look, I accept different politicians will have different views."
Without a change of heart from New Zealand's right-leaning politicians, the reform will fail.
Lowering the voting age at a national level requires 75 per cent support in parliament and the opposition National and ACT parties - which hold 33 and 10 seats respectively - have ruled out support.
"We've got to draw a line somewhere and we're comfortable with the line being 18," Opposition Leader Chris Luxon said.
ACT leader David Seymour pointed to a recent TVNZ poll that showed only 13 per cent of Kiwis wanted the change, which he called "judicial activism".
"We don't want 120,000 more voters who pay no tax voting for lots more spending," he said.
"The Supreme Court needs to stick to its knitting."
The Maori Party and the Greens support the change, with Greens spokeswoman Golriz Ghahraman calling the decision a "massive win for democracy".
Voting is optional in New Zealand and in recent years young people are increasingly choosing to turn out at general elections.
While only 63 per cent of enrolled 18- to 24-year-olds cast a ballot at the 2014 election, that jumped to 69 per cent in 2017 and again to 78 per cent in 2020.
However, the number of under 25s choosing to vote is below the overall turnout, which was 82 per cent at the last election.
A clutch of countries allow 16-year-olds to vote including Argentina, Brazil, (where voting is compulsory between the ages of 18 and 70), Austria, Malta and Scotland.
A few more, including Greece, East Timor and Indonesia, set the minimum voting age at 17.
Ms Tipler said 16-year-old Kiwis deserved the right.
"At 16, you can work part-time ... you're paying tax ... you can consent. You can learn to drive," she told Radio NZ.
"All these things means at 16 it makes sense as the voting age rather than 18."
The Supreme Court ruling marks the end of a multi-year fight by Make It 16 through New Zealand's court system.
In October 2020, a High Court judge declared the voting age of 18 was a "justified limit" and last year, the Court of Appeal declined to rule, labelling it a "quintessentially political issue".