National is hitting out at Stats New Zealand for withholding Census information.
Last year's Census, the first done online, was plagued with controversy around people not receiving their forms and low participation rates.
Now, Chief statistician Liz MacPherson is refusing to disclose how many took part in last year's Census.
The Governance and Administration Select Committee has twice asked for the figures, and is considering forcing her to release them.
Select committee member National MP Nick Smith told Larry Williams they need to know the numbers, to allocate funding.
"This is the period over the last five years we've had the fastest population growth in New Zealand history, so getting accurate numbers is pretty critical."
He says that MacPherson's argument that the numbers need proper context sounds like a lot of "gobbledegook".
Smith wants to know how many people actually finished the Census.
"If we're going to be able to rely on the population, income, all these other stats, that's pretty important information."
Smith says that they have written to her warning that she will be found in contempt if they do not release that figure.
Both parties are united in their outrage with her take, Smith says.
One of the issues with this Census was the reliance on it being online.
"The Australians did their Census in 2016 on the same basis. They did it successfully. Ours has been a pretty big stuff-up. We need to get to the bottom of what occurred."