Chief Ombudsman Peter Boshier has written to Jacinda Ardern with his view on publishing the 33-page coalition document that she has refused to release, asking her to respond within five days.
He has also made a general plea for advisers to ministers and top officials to stop "dumbing down" advice in an effort to spare them from potential embarrassment.
Ardern has been under pressure from the Opposition to release the 33-page document, which she describes as an unofficial "record of some of our [coalition] conversations".
Deputy Prime Minister Winston Peters described it as a "document of precision on various areas of policy commitment and development" and "directives to ministers with accountability and media strategies".
The Opposition has sought to portray the Government as secretive, urging Ardern to release the document while accusing ministers of refusing to answer simple questions - which has seen the Opposition lodge more than 6000 Parliamentary written questions.
Ardern's refusal to release the document is now the subject of a complaint to the Office of the Ombudsman.
Boshier told Radio New Zealand's Nine to Noon that he had read the document.
"I've written to the Prime Minister and my expectation is a five-day time turnaround for a reply."
He said he could not talk about this individual case, but described the general process.
"I set my own timelines as to what's appropriate. 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?'
"And then I release my decision. It's very rare that my decision is not complied with."
Ardern said in a Facebook Live video last night that she wanted to be more transparent and release Cabinet papers and official advice that lead to a decision.
"We're doing work on that now so we can improve transparency around that decision-making, whilst at the same time making sure that we still get really free and frank advice from our public servants," Ardern said.
Boshier was encouraged by the Government's approach, saying that a culture of transparent Government had to start with strong leadership.
But there had been a risk-averse approach that had seen officials shy away from provocative advice that might cause political embarrassment.
"I would like briefings to ministers to be more robust and to be able to be much more provocative than has occurred because of a dumbing down of advice in the event that it might be released."
There had also been occasions when officials had wanted to release information, but minister's offices had "frustrated that process", as well as unjustified redactions from documents that had been released.
He said it was wrong to characterise the Office of the Ombudsman's sanctioning powers as a slap on the wrist with a wet bus ticket.
"In my two years, I've not had any decision that's not been complied with ... People hate being reprimanded by the Ombudsman. In my experience, they'll do anything to avoid public criticism."