Prime Minister Jacinda Ardern says under no circumstances is it acceptable for government departments to include questions about New Zealanders' political persuasions in surveys.

Photo: Supplied

Inland Revenue has admitted it was wrong to include the question in the research about the public's view on fairness in the tax system.

State Services Minister Chris Hipkins has asked the State Services Commissioner Peter Hughes to investigate.

Photo: RNZ / Rebekah Parsons-King

Ms Ardern said she was only told about the IRD survey this morning and if there were other examples of it happening, it needed to end.

She said it was appropriate for the State Services Commission to provide guidance and while there would be legitimate cases where undertaking research was necessary, it was not appropriate to attach political questions.

Mr Hipkins said he was concerned to read in the media that the survey included political questions.

He said he suspected it was an error of judgement, but he has asked Mr Hughes to follow up with the department.

IRD's admission has come just days before the release of a major report on possible tax reform.