Anything short of releasing Julie Anne Genter's secret letter isn't "good enough", the Opposition says.
The Chief Ombudsman has weighed into the long-running saga, ruling the Associate Transport Minister and Green MP was right to withhold the letter she penned over the Let's Get Wellington Moving project.
The letter Genter sent to Transport Minister Phil Twyford this year has been the subject of huge speculation over just how much influence the Greens had on shoving a second Mt Victoria tunnel on the back burner.
In his decision, the Ombudsman recognised the confusion the letter had created when it landed in the House.
That included Genter saying she wrote the letter in her capacity as a Green Party transport spokesperson, but subsequently confirming she wrote it on Ministerial letterhead signed by her as the Associate Minister.
"The statements in the House generated significant public and parliamentary debate, as well as confusion, public disquiet and speculation", the Ombudsman said.
Wellington based National list MP Nicola Willis said: "Against that backdrop of, I think, misleading people, why should we trust her [Genter's] summary of what's in the letter, we deserve to be able to examine her full words in their full context."
The Ombudsman took issue enough with the confusion to order Twyford and Genter to issue a clarifying statement.
"The Associate Minister advised that she was comfortable supporting this package if a number on matters were clarified, including that the public transport, and walking and cycling components of the package would be completed as soon as practicably possible and that work on rapid transit be prioritised ahead of the second Mount Victoria tunnel", they said.
Willis sees that as an admittance of the significant role Genter played in the sequencing of the project by "demanding" the delay of the tunnel in return for her support.
National's Transport spokesman Chris Bishop said the problem wasn't Genter providing feedback that she wanted mass rapid transit prioritised over roading projects.
"What remains a mystery is why doesn't Julie Anne Genter just be honest about this rather than dance on the head of a pin, using every excuse under the sun to keep her letter secret?"
Opposition MPs have spent months trying to get information about the nature of the letter out of Genter after she refused to release it.
Twyford said in a statement today that in a coalition government all major policy decisions were discussed with support parties and LGWM was no different.
"Successive Governments have recognised discussions on Cabinet decisions need to take place in confidence to ensure the best decision is made," Phil Twyford said.
"We supported releasing a statement to put to rest the false speculation whipped up by opposition MPs about the letter's contents," Genter said.
In his decision, Chief Ombudsman Peter Boshier said the letter was right to be withheld in order to maintain the effective conduct of public affairs through the free and frank expression of opinions between Ministers, and between Ministers and political parties.
"In my opinion, disclosure of the letter would discourage political parties and Ministers from expressing their views on draft policy papers in writing or as clearly and frankly as they might do in an environment of trust and confidence."