State Services Commissioner Peter Hughes has written to the chief executives of government departments to remind them about the importance of political neutrality.

This follows his announcement of details of his examination of the circumstances which led to Inland Revenue commissioning a public poll that included a question about the political leanings of taxpayers.

State Services Minister Chris Hipkins has asked Mr Hughes to examine what happened and to provide an assurance that the principle of political neutrality is understood.

Mr Hughes' letter says political neutrality is central to a Public Service that is always fit to serve the Government of the day and successive governments.

"The principle of political neutrality is about State servants doing their jobs professionally and without favouring, or creating the impression of favouring, one political party or point of view over another. Perception can be just as damaging to public trust and confidence as reality."

Mr Hughes says he will form a view on the Inland Revenue matter once he has considered the facts, which is expected to take about six weeks.