The Ombudsman Peter Boshier has written to Prime Minister Jacinda Ardern about the extended "unofficial" coalition document.
The existence of the document was first acknowledged by Winston Peters, who said it would be released "at some point".
Since then, the Government has backpedalled, refusing to release the document under the Official Information Act, saying it's not held by Ministers.
Newsroom journalist Sam Sachdeva, who lodged the OIA, took the issue to the Ombudsman.
Mr Boshier told RNZ he has written to Ms Ardern and expects the Prime Minister to respond within five days.
While Mr Boshier wouldn't say what the contents of the letter are, he said in his two years as chief Ombudsman, every decision he's made has been complied with.
Outlining the general process, Mr Boshier said, "I see the document. I go through it. I form my own view. I then take that provisional view to each side and say, 'This is what my view is. What do you say in relation to my view?'"
The office of the Ombudsman has confirmed the contents of the letter are preliminary, outlining that a complaint has been recieved.
During the half-hour interview about Government transparency on RNZ, Mr Boshier said the OIA is a "fundamentally important part of New Zealand's framework."
"Like a lot of laws, it needs enforcing, and it needs a will and it needs good leadership," he said.
He said there is too much risk adversity in the release of information and the Office of the Ombudsman often finds unjustified redactions of information.
He's concerned Ministers are not being given free and frank advice, saying it's being dumbed down out of fear the advice will go public.
Consideration also needs to be given as to when blue-sky ideas become subject to the Official Information Act, he said.
"Some ideas at the beginning are silly... blue sky ideas that go nowhere," so he said discussion of when on the timeline such ideas would become subject to an official information request needs to take place, he said.