Prime Minister Jacinda Ardern and Deputy Prime Minister Winston Peters signed a coalition agreement in public last month - but a more detailed document is being kept behind closed doors.

This story was originally published on Newsroom.co.nz and is republished with permission.

The Government is refusing to release a secret document with directives for new ministers, despite Deputy Prime Minister Winston Peters promising it would be made public.

National leader Bill English has called for the agreement to be made public, saying it is "at the heart of the governing arrangements" for the new Government.

KEVION STENT/STUFF "It's a bad start for a Prime Minister and Deputy Prime Minister who have promised to be a more transparent and open Government," Bill English said.

The existence of the 38-page document was first revealed by Peters the day after Labour and New Zealand First signed a more slender eight-page public coalition agreement.

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Speaking to media after the allocation of ministerial portfolios, he described it as "a document of precision on various areas of policy commitment and development".

"These are directives to ministers with accountability and media strategies to ensure that the coalition works, not in a jealous, envious way, 'We got this and they got that', but as a government successively, cohesively working.

"We've put a lot of thought into it, in fact day one of our negotiations that was the first subject we raised, how are we going to handle a cohesive coalition arrangement?"

At the time, he said the document was still being finalised, but would cover the appointment process for diplomats.

Peters said then the document would be made public, saying it was "for the province of the Prime Minister to release".

However, in response to an Official Information Act request from Newsroom seeking the document's release, Jacinda Ardern's adviser Heather Simpson claimed "the Prime Minister does not hold any such official information".

Simpson's letter referred to Section 2 of the Act, saying official information covered only information held by "a Minister of the Crown in his official capacity".

The Ombudsman's OIA guidelines for ministers state that while official information does not include information held by a minister in their role as a member of a political party, "such information may become official information if it is subsequently used for official ministerial purposes".

Newsroom has appealed the Government's decision to the Ombudsman.

Wellington lawyer Graeme Edgeler said the document appeared to qualify as official information based on Peters' description of it.

"It's going to govern how he technically appoints ambassadors and other people overseas, which would be the Cabinet committee on honours and appointments, well that's something they'd be using if it's correctly described."

While an agreement that covered the parties' political or parliamentary roles would be exempt from the OIA, that did not appear to be the case here, Edgeler said.

"If ... it is going to cover things that the Government is doing as the Government, not as MPs in the House, then I can't see how this could be refused on the basis it's not about ministers."

English said the document was "clearly official information" and should be released, given the public's need to understand how the new coalition would be run.

"It has to be made public because it's at the heart of the governing arrangements that New Zealand's just signed up to...

"It's a bad start for a Prime Minister and Deputy Prime Minister who have promised to be a more transparent and open Government."

The Opposition has already lodged over 6000 written questions with the Government, "setting a baseline against which we can hold them to account", and had already found it difficult to get a response to some questions, English said.

"We're finding they are not taking the business of government seriously, they don't seem to understand that part of being a Government is being sufficiently organised to provide the information, so right now I think you'd say they're just too disorganised to do it - I hope it's not an indication of how they're going to run the Government."

English said the Government would struggle with the new level of transparency that he argued the last National Government had implemented.

"We pushed hard on data and transparency and public servants having to be open...now we weren't perfect, and you guys didn't give us any credit for it, but we did shift the ground a long way."

A spokesman for Ardern said the coalition agreement which had been publicly released was "the only official document that guides the agreed work programme of Labour and New Zealand First in Government".

This story was originally published on Newsroom.co.nz and is republished with permission.