An Otago census field officer has come forward with a scathing description of its delivery operations.
Initial figures show one in 10 people did not take part in the census, which was conducted in March.
Field officer Islay McLeod, who has worked in the past three census counts, called the census delivery "inefficient".
"The key issue for me was it was so bloody frustrating and completely unnecessary half the stuff I was doing," Ms McLeod said.
"I think the stats department was sold a pup."
Ms McLeod said the census delivery was a "shambles" after changes were made to shift the systems online for the first time this year.
In previous years, Ms McLeod said she was given an area to cover.
However, for the 2018 census, field officers were given a block of addresses often along one side of the street, she said.
It was not unheard for multiple field officers to cover the same street days apart, Ms McLeod said.
She was speaking from experience.
After arriving home to find a census envelope, Ms McLeod was then asked to cover the opposite side of her street two days later.
"The problem is operational," she said.
When contacted by RNZ for comment, Stats NZ declined, saying the appropriate spokesperson was unavailable until next week.
Government statistician Liz MacPherson said, in a previous interview with RNZ about census response rates, Stats NZ already knew it did not get everything right.
"We built new systems and processes to run this census, and while the majority of New Zealanders were able to take part without a hitch, we know that some people did not have a good experience this year," Ms MacPherson said.
"I have had mixed feedback from people. For some it was the easiest census ever; for others it has been a frustrating experience. For that, I am sorry."
Meanwhile, Ms McLeod recalled shoving envelopes under doors.
The system did not cater efficiently for households without a letterbox or internet, she said.
Field officers were not given hard copies to help anyone, Ms McLeod said.
Instead she said people were forced to wait on the phone for up to 20 minutes to arrange for a hard copy to be delivered to their home.
They were given uniforms, emergency beacons and a flashing light for the top of their cars.
Once a rite of passage for older generations, Ms McLeod said taking part in the Census was now viewed as more of a chore.
Despite all of this, she said she still believed the data from the census could be trusted.