The Government's internal watchdog says an Inland Revenue survey asking for people's political preferences was disappointing and "ill-judged".
But the State Services Commission (SSC) said it had found no evidence to suggest that IRD asking people to rate their political affiliations was politically motivated.
Nevertheless, the commission has written to all public service chief executives, requiring them to ensure all public surveys undergo a specific check for political neutrality.
In a survey last year, IRD asked people to rate their political affiliation on a scale of zero to 10 – with one being "extremely liberal" and 10 being "extremely conservative".
Prime Minister Jacinda Ardern said those sorts of questions should never be attached to any research from government departments and they were "just not appropriate".
National's then finance spokeswoman Amy Adams said the question did not go to the core business of the IRD and requested that the SSC conduct a formal investigation.
The investigation into the survey was released today and concluded although the question was not politically motivated and was an isolated incident, it was disappointing that the question was asked.
"I'm disappointed this has happened," SSC Deputy Commissioner John Ombler said.
"It is never okay for a government agency to seek or collect information on the political leanings or party affiliations of citizens."
He said the questions asked were "ill-judged, inappropriate and had the potential to undermine the principle of political neutrality".
Ombler said it was also disappointing political neutrality was not at the front and centre of the work and thinking behind these surveys.
"Someone should have asked the question."
The questions, he said, were motivated by "academic rigour" such as the IRD wanting to better understand the tax system and the Department of Conservation wanting to have a better grasp of people's thoughts on pest control.
It also helped Stats NZ to develop an effective marketing campaign for the 2018 Census, Ombler said.
"I don't doubt research on these surveys shows the results might be more meaningful in a broad sense if questions of a political nature are included.
"But this cannot be at the expense of political neutrality, which is the overriding consideration in the Public Service."
Ombler said the incident should serve as a timely wake-up call.
The SSC has asked all public service chief executives to ensure all public surveys undergo a specific check for political neutrality.
He also wrote to the Public Service functional lead on data, Liz McPherson, and asked her to work to help ensure any issues around political neutrality is well understood across government.