On Tuesday, Labour MP Soraya Peke-Mason was sworn in as the replacement for outgoing speaker Trevor Mallard, becoming the 60th woman in the 120-MP house of representatives.

With a vacancy in Hamilton West, it means there are 60 female MPs to 59 men in the chamber, giving Kiwi women the edge.

Acting Prime Minister Grant Robertson - deputising for Jacinda Ardern as she attempted to travel to Antarctica on Tuesday - said the occasion was worthy of celebration.

"It is a significant moment in the democratic representation of New Zealand," he said.

"At a time when we have a female prime minister, Governor General and Chief Justice, it is further evidence of the strides that we're making in gender equality."

UN Women and the Inter-Parliamentary Union, which keeps data on the makeup of national parliaments, makes New Zealand the sixth country to achieve equal representation in 2022, behind Rwanda, Cuba, Nicaragua, Mexico and the United Arab Emirates.

Australia's parliament has 38.4 per cent women - up from 29.8 per cent prior to the last election.

New Zealanders are proud of its trailblazing role in giving women the vote, becoming the first self-governing country to do so, in 1893.

However, the right to stand in Kiwi elections did not come to women until 1919, and it wasn't until 1933 that one was elected: Elizabeth McCombs, who replaced her deceased husband James at a by-election in Lyttleton, near Christchurch.

When Helen Clark, prime minister from 1999 to 2008, was first elected she was just the 17th female MP that Kiwis sent to Wellington.

Ms Peke-Mason will be the 177th.

"Good things take time ... no doubt it's a special day for me but it's also a historic occasion for Aotearoa New Zealand," she said.

Just as in Australia, New Zealand's left-of-centre parties typically preselect more female candidates than conservatives.

Of its 64-strong caucus, 37 NZ Labour MPs are women, and seven of New Zealand's 10 Greens MPs are also women.

The milestone has sharpened the disparity with the opposition National party, which boasts just 10 women MPs of its 33 representatives.

Opposition leader Chris Luxon, who described Tuesday's milestone as "brilliant news" said he wanted more diversity to his National partyroom.

"I've been really upfront since I've come to Parliament as (National's) leader that we've got a lot of work to do," he said.

"I did a lot of work in that space before coming to politics in corporate New Zealand ... to make sure we're getting rid of unconscious bias and opening up to new talent pools."

The 2020 election also gave New Zealand the unlikely title of queerest parliament in the world, with 12 openly LGBTQI representatives elected: all within the Labour and Green partyrooms.

Australian Associated Press