The knives are out over the 2018 census after it was revealed important data is missing.
Around 700,000 people did not complete the 2018 census, which could have some major ramifications in New Zealand.
- 700,000 Kiwis didn't complete census
- Concern over low cturnout
- Simon Bridges 'losing faith' in official numbers
Information from the census is used for a lot of population-based decisions, including electoral borders, and DHB funding.
Stats NZ tried to plug the holes with existing Government data, but there were some areas that can't be made up.
Government statistician Liz MacPherson told The AM Show the data for electoral borders and DHB funding was fine, but there were some areas where it couldn't be fixed and the data is unusable.
One of those areas is iwi affiliation, which Massey University Professor Paul Spoonley told The AM Show is a huge loss.
"No iwi affiliation data and a lot of Māori groups and organisations and iwi are going to be quite significantly affected by that.
"That's a real hole."
Māori council chief executive Matthew Tukaki agreed, and told Newshub the flow-on effects will be deeply felt.
"We're not able to get on top of all the massive number of social issues that these communities face if the data isn't accurate."
Fewer people filled out the census last year because it was the first time it was online only, something Dr Spoonley called a gamble.
"Moving sort of cold turkey into a system in which we required people to enter their data online was a big gamble and I'm afraid that gamble did not pay off."
He said the previous National Government, which made the decision to move the census online, gave an extra $30 million in funding for the census, but it wasn't enough.
"It was short in terms of funding, and it was a bit of an experiment which really did not pay off."
Prime Minister Jacinda Ardern agreed and the Government has already poured an extra $10 million into Stats NZ for the 2023 census.
"It is true to say that Stats NZ transferred to a predominantly online mechanism last time, they also said look we need to be prepared for there being some failures in this massive change in operation," Ardern told The AM Show.
"Instead of the last Government preparing for that and providing funding for it, they actually told them to reduce down their costs by 5 percent."
MacPherson said Stats NZ did the best they could considering the circumstances.
"We had the money that we had and we've made good use of it."
She admitted there were some people that weren't reached by the online method, even if they had the means to fill it out.
"Let's face it we know that for some people even if they do have access to the internet they don't want to do it online, so how do we make it [work]."
But she said it's a catch 22, because the census can't stay on paper forever.
"If we hadn't gone online we would probably be having questions about why we weren't going digital, so the question is how we get the best mix of both going forward."