David Bain is asking the Ombudsman to intervene in his claim for compensation to direct that Justice Minister Judith Collins release the confidential report by former Canadian judge Ian Binnie to him.
That way his team will be able to assess whether Mr Binnie made errors in law, according to Mr Bain's lawyer, Michael Reed, QC.
Ms Collins' predecessor, Simon Power, commissioned the report after Mr Bain claimed compensation in 2010.
Yesterday she trashed Mr Binnie's report and explained why she believed it needed to be peer reviewed by New Zealand QC and former High Court Judge Robert Fisher.
"My concerns are broadly that the report appeared to contain assumptions based on incorrect facts, and showed a misunderstanding of New Zealand law," Ms Collins said. "It lacked a robustness of reasoning used to justify its conclusions."
She said she was not prepared to take the report to the Cabinet without being peer reviewed because she did not believe it would stand up to public scrutiny.
She rejected any notion that she was "shopping around" for an opinion she liked.
Mr Fisher was not taking a look at the case as a whole but at the way Mr Binnie reached his conclusions.
The Herald revealed in September that Mr Binnie's report had concluded that, on the balance of probabilities, Mr Bain was innocent of murdering his parents, brother and two sisters in Dunedin in 1995, for which he served 13 years' imprisonment.
Mr Reed said it was unfair that Ms Collins consulted the Solicitor-General on Mr Binnie's report - before referring it to be peer reviewed by a former New Zealand judge - and refused to hand it over to the Bain team.
Mr Reed described the Solicitor-General as an "opposition" lawyer, the one that had lost his case at the Privy Council.
"Now when she gets a report of Justice Binnie, she keeps it secret to herself and then she seeks advice from our opposition lawyers."
He said the report could not be described as "legally privileged - that is a legal nonsense", he told Radio New Zealand.
A complaint has been made to the Ombudsman on the basis that the report comprises personal information about David Bain and he is entitled to it.
The Ombudsman has the power to direct a minister to reveal any document in the minister's possession, a directive which can be overturned only by the Cabinet, which has already had its final meeting of the year.
Mr Bain's longtime advocate Joe Karam told the Otago Daily Times the process was an "affront to natural justice".
He had spoken to Mr Bain last weekend and said he was "very, very upset".
He had had a "terrible week" following revelations last Monday that Ms Collins was getting more advice.
"He just said, 'When is this ever going to end, I have been interviewed under oath by Justice Binnie for a whole day, found not guilty in a court of law by a jury, and found there was a miscarriage of justice by the Privy Council at my first trial ... what more can I do, it is still going on and it is all being played out in the media."'
Ms Collins said she raised concerns directly with Mr Binnie at a meeting on September 13 at which Justice Secretary Andrew Bridgeman was present.
"I advised him I would be getting the matter peer reviewed."
Mr Binnie had since sent her two unsolicited further final reports for which he would not be paid.
Mr Binnie has received $413,764 for professional services and expenses.
Ms Collins is expecting to receive Mr Fisher's report by the end of the week and said it would then be clearer what the next step would be.
Mr Binnie, a retired judge of the Canadian Supreme Court, did not respond to requests for comment.By Audrey Young Email Audrey