She said if this had been happening in other areas of Government, then it should end.
But she said she hadn't heard of this occurring anywhere else within the Government.
Over the weekend, Stuff revealed the IRD had asked questions about whether people sit to the right, or the left of the political spectrum in a poll about globalisation and fairness in the tax system.
National finance spokeswoman Amy Adams wrote to State Services Commissioner SSC Peter Hughes this afternoon, asking for the department to conduct a formal investigation into the questions.
The question was met with outrage by some, including the Taxpayers' Union which said it raised "serious questions".
Hipkins said he was "concerned" to hear about the question being included in the survey.
"I suspect it was an error of judgement, but I have asked Mr Hughes to follow up with IRD," he said in a statement this afternoon.
"The political neutrality of the public service is paramount and I want to ensure that the message is reinforced.
Earlier today, a spokeswoman for Revenue Minister Stuart Nash said the Minister had no knowledge of the poll or the wording of the question.
In fact, she said it was the Minister's understanding that Colmar Brunton wrote the question and suggested it be included in the survey.
The spokeswoman said Nash had discussed the issue with the IRD's Commissioner, Naomi Ferguson, this morning – she was also unaware of the survey question.
"They both agreed it was an inappropriate question," she said.
She added that the Commissioner was now having a closer look at IRD processes and the question has been deleted from the survey.
Colmar Brunton had been advised not to report on the question when it presents the findings to IRD, the spokeswoman said.
Colmar Brunton said it does not comment on client projects.
In the letter to Hughes, Adams said a significant number of the questions in the survey do not go to the core business of the IRD.
"Therefore [this] raises several questions regarding their independence and how these questions came to be included in a publically funded poll for a core part of the state service."
What's worse, she said, is that the saga occurred just a week before the highly anticipated Tax Working Group report goes before Cabinet, before being released to the public days later.
Not only does Adams want an investigation into the IRD over the incident, she wants the Government to take a look at all its departments and ministries to see if any similar polling had been conducted.
In a response to questions from the Herald, put to the IRD this morning, the department said this afternoon it would not be commenting as the matter was now being looking into by the SSC.
