Jacinda Ardern pictured maskless among a large crowd has drawn the ire of several past and present politicians.
The Prime Minister posed for the photo on Tuesday with the 120 youth MPs, Governor-General Dame Cindy Kiro, and a number of sitting MPs on a staircase in the Beehive. Just one person can be seen wearing a mask.
A spokesperson for the Prime Minister said Ardern had been wearing a mask the rest of the day but took it off briefly for the photo at the request of the photographer.
Other photos in the social media post that Ardern made show the Prime Minister and others wearing masks.
ACT leader David Seymour said the least Ardern could do is follow Parliament's mask rules.
"It sounds like the Prime Minister may have got confused. She may have thought she was still overseas," he told Newshub.
"She has asked New Zealanders to follow her rules at great cost. The least she could do is follow Parliament's rules herself."
Former Prime Minister Helen Clark said it was shocking to see all the unmasked people.
"Indeed shocking to see the unmasked youth parliament. What on Earth are they thinking. NZ is in the middle of a pandemic surge," she tweeted.
New Zealand First leader Winston Peters called the photo hypocritical.
"The PM and a number of MPs who like to lecture Kiwis on wearing masks. Then walk out the door and this is what they do - because it suits them," he tweeted.
Earlier on Tuesday, epidemiologist Professor Michael Baker said he was "quite shocked" to see the image and that it was a "missed opportunity to promote mask-use".
Prof Baker said New Zealand needs its leaders to help normalise mask use.
An hour after the Prime Minister posted the photo to her Instagram and Facebook accounts, Speaker Trevor Mallard emailed everyone in the Parliamentary precinct a reminder about wearing masks.
"For the safety of all on the precinct, I remind you of this rule. It applies to everyone. I have asked the CE of Parliamentary Services to advise me if anyone is not cooperative."
Mallard told Newshub his email reminder was not connected to Ardern's social media post.
Last week, COVID-19 Response Minister Dr Ayesha Verrall and Director-General of Health Dr Ashley Bloomfield urged the public to wear masks more. They said mask-wearing should be done not just for themselves, but also for others.
"Mask-wearing should be like wearing a seatbelt," Dr Bloomfield said.
"What we mean when we recommend mask-use is that you should do it," Dr Verrall added.
The Prime Minister previously got into hot water over mask-use on the 2020 election campaign trail for taking a maskless selfie with fans.
She said at the time that the selfie was a "mistake" and that "it was the wrong thing".