Statistics Minister Deborah Russell says more than $125,000 has been spent on the Warriors promotion intended to incentivise New Zealanders to fill in the Census.
ACT says it's "not even in the realm of sensible and targeted spending", but Russell said the value of getting people to fill in their papers "far exceeds" the cost.
Kiwis who rolled up to Mt Smart Stadium on April 30 and filled in a Census form were rewarded with free tickets to a Warriors match, a $25 food and drink voucher, and an entry into a draw for four people to go to Australia.
The purpose is to get more people to fill in the Census, especially with lower than desired response rates among Māori and Pasifika and in south Auckland.
Under questioning from ACT's statistics spokesperson Damien Smith in the House on Thursday, Russell said $150,000 had been budgeted for the promotion and the cost so far sat at $126,694.
She couldn't yet say how many people had entered the draw as the promotion remained open until the end of the week.
"We need to do everything we can, in the final stages of collections, to help reach all communities which might not otherwise participate in the Census. The value of the data far exceeds the amount that is spent on arrangements like this."
Smith asked Russell if she believed the spending was fair considering people who filled in the Census on time "got no rewards", while those who didn't were able to get free tickets and potentially a trip to Australia.
The minister responded by saying most Kiwis had completed the Census, but more responses were needed "in order to get a viable and robust response".
"That is why we are taking whatever steps necessary to ensure that people do the Census, and if that takes promotions and the like, then that is what we will do in order to get the Census completed."
She said that currently the completion rate for the Census sat around 87 percent and is "continuing to go up day by day".
"The acceptable result is one that gives us a robust dataset going forward into the future, for decisions to be made for our communities. Stats NZ is confident that, together with the raw forms returned and the subsequent addition of administrative data, we will have an excellent completion rate."
Russell said that, in terms of costings, "we know that the return from completing the Census, from getting this work done, is a return of roughly 4:1 in terms of the capacity that people have to make decisions going forward based on an excellent dataset".
She wouldn't rule out using other promotions or incentives to get people to complete the Census in the future.
"There are standard processes for encouraging people to complete the Census. At this stage, it is a matter of people doing their civic duty and incentives. Going forward, we will be looking at prosecutions, but that is an operational matter for Stats NZ to pursue.
"In terms of what we do with the next Census, that will depend on the evaluation of this Census, and that won't be completed for a long time yet."
In a statement following the exchange, Smith took issue with the "gimmick".
"What Labour can't comprehend is that there are ways to do things that don't involve bribes and spending other people's money. For example, ACT suggested that beneficiaries should have to fill out their census form for them to continue receiving their benefits."
StatsNZ Deputy chief executive of census and collections Simon Mason previously told RNZ the Warriors promotion had been a "really successful part of our engagement".
He said he had heard from people who had taken part in the Census that hadn't done so before attending those events.
Earlier this month, Russell wouldn't commit to a 90 percent response rate for the Census.
"I'm certainly committed to getting the Census done and I am committed to what Stats is doing to get the census across the line," she said.
Census collectors will remain in areas affected by Cyclone Gabrielle (the Far North and Te Tairāwhiti and Hawke's Bay regions) until June 1.
The last day people could fill in census forms online before receiving a final notice was May 4.