The Ombudsman is re-investigating whether a "secret letter" penned by Green MP Julie Anne Genter about Wellington's multi-billion-dollar transport plan should be made public.
Genter wrote the letter in 2019 when she was also the Associate Minister of Transport.
She sent it to then Transport Minister Phil Twyford during pre-consultation on the Let's Get Wellington Moving indicative package draft Cabinet paper.
The letter became the subject of controversy and landed in the House for days on end as speculation grew it was the reason a second Mt Victoria tunnel was put on the back burner.
Chief Ombudsman Peter Boshier ruled at that time Genter was entitled to withhold a copy of the letter to maintain the effective conduct of public affairs through free and frank expression of opinion.
However, Boshier made Genter issue a clarification because he considered statements she made in the House waived the confidentiality of the letter to some extent.
Now, the letter has been re-litigated after Genter tweeted about it in June 2020.
She tweeted: "My letter that totally predicted the unaffordability of the package, especially the highways components, and called for mass transit to be prioritised bc [sic] it would do more to enable people to get quickly around the city and region with lower emissions?"
National MP Chris Bishop asked now Transport Minister Michael Wood to release the letter under the Official Information Act (OIA), in light of Genter's tweet.
Bishop argued the tweet revealed more information about the letter than previously disclosed and was therefore another waiver of confidentiality.
"Surely it is an indication of the low level of confidentiality that Ms Genter attaches to the communication if she is now willing to just tweet more information about it in this way?", Bishop wrote.
But Wood declined to release it, again citing the need to protect free and frank expression of opinion.
"I note this approach is consistent with the findings in the report of the Chief Ombudsman to which you refer", he said in response to Bishop's OIA request.
Bishop then complained to the Ombudsman, who has started an investigation by writing to Wood's office yesterday.
Bishop said he was pleased the Ombudsman was looking at the issue again.
"After four and a half years of talk, there has been no progress on a second Mt Victoria tunnel. Julie Anne Genter's secret letter to Phil Twyford is a big reason for that and the public deserve to know exactly what she said to the Minister that helped delay the project."
The clarifying statement issued in 2019 said Genter was concerned about inducing traffic and the resulting increased congestion, greenhouse gas emissions and undermining of demand for public transport.
She was also concerned about there being sufficient funding available for public transport.
"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."
Both the Green Party and the Transport Minister's office have been approached for comment.