The government is investing more than $16 million in Stats New Zealand in this year's Budget to help fix the mistakes made in last year's Census data.

Photo: RNZ / Rebekah Parsons-King

Today Stats NZ announced it will begin releasing data from 23 September.

This follows two unprecedented delays, due to a low turnout in which nearly one in seven people did not complete Census 2018.

Statistics Minister James Shaw said it was unlikely Census 2023 could be conducted successfully under the current budget.

"I, as Minister of Statisitcs, and this government are not willing to gamble with the next census which is why the funding announced today for this year's Budget will help to get ahead of the process to ensure the next census runs more smoothly and delivers the outcomes New Zealanders expect and deserve,'' he said.

"The previous National-led government decided to shift the Census to a mostly online survey and, at the same time, directed Stats NZ to cut costs over two census cycles.

"Stats NZ has now confirmed it will provide reliable, quality 2018 census data to calculate how many electorates will be needed for next year's General Election and to revise electorate boundaries where necessary," Mr Shaw said.

He said Stats had to delay other work and re-allocate funds to get its data up to scratch and the resulting $5.76m shortfall will be covered in this year's Budget.

"There's also Budget approval this year of $10.36 million to enable Stats NZ to get ahead of the next census. The money will develop the business case for the 2023 Census and start development work on it."

Prime Minister Jacinda Ardern said that while it was positive Stats managed to pull through, it was not an ideal scenario.

The National Party said it was an utter shambles that 2018 Census data would not be released until almost a year after the first deadline.

Its statistics spokesperson Jian Yang said it was staggering how poorly organised and executed the Census was by Stats NZ and the current government.

"Not only are we missing key data, but some of the data we do have is going to be substandard.

"Iwi affiliation information is particularly important for us to better understand the socio-economic difference within Māori and to facilitate ethnic reconciliation.

"The Census is also our only source of detailed socio-economic information about local communities and other small population groups, such as migrants, children, older people, and single-parent families", he said.

The amount of funding and decision for the Census to go online was made by the previous National government.

Mr Yang said by the time they release all the data it will likely be out of date.