Justice Minister Judith Collins outlined to Parliament on Tuesday some of the issues she has with a retired Canadian judge's report on the David Bain compensation claim.
Ms Collins is getting Justice Ian Binnie's report peer reviewed, saying it makes assumptions based on errors of fact, and that it shows a misunderstanding of New Zealand law.
She cited examples in Parliament, saying Justice Binnie made an assertion about evidence in Mr Bain's trial, which was later clarified in the retrial.
The minister says Justice Binnie has also assumed that Mr Bain's supporter, Joe Karam, was correct in his view that adverse inferences should be drawn against the Crown's case on evidence that is no longer available.
"This is incompatible with the onus of proof being on Mr Bain in this particular case because this is in fact a request for Cabinet to use its discretion and that's very clearly wrong."
Ms Collins says she's awaiting the peer review before deciding when to release that and Justice Binnie's report.
Mr Bain spent 13 years in jail for the 1994 murders of his parents and three siblings, before he was acquitted at a retrial in 2009.
Justice Binnie says the minister is playing politics over the claim and is acting unfairly.
He told Radio New Zealand News he retained an eminent New Zealand counsel to make sure he did not confuse elements of New Zealand law with Canadian law and took his advice.
In an email to New Zealand media, the judge says he expected the minister to follow a fair and even-handed process, yet she has taken advice from the Solicitor-General who for almost 17 years tried to uphold the guilty verdict from David Bain's first trial.
Justice Binnie says the minister is searching for reasons that support her preferred disposition of the Bain claim.
The judge says that by insisting his report remain confidential, Ms Collins seems to have a "curiously one-sided view of confidentiality".
He says it is unfair that his report has been given to police and other officials but David Bain has not seen it. He believes the report should be made public so people can judge the merits of the minister's concerns.
The lawyer representing David Bain, Michael Reed QC, says Ms Collins has unfairly attacked the judge and her actions make New Zealand appear a banana republic.
"She's been slagging him off for the last few days, which is quite unprecedented behaviour for a Justice Minister against such an eminent judge." Mr Reed said it was entirely understandable Justice Binnie had made some "measured comments" about his report.
Mr Reed said the report should have been accepted and the only thing the minister should be considering is how much is paid in compensation.
He has laid complaints with the Privacy Commissioner and the Ombudsman to try to get the report released publicly.
Green Party co-leader Metiria Turei says the minister should not continue talking about the failures of the report and attacking its author without releasing the document.
"That is grossly unfair, it's un-ministerial and is not the behaviour we would expect of a minister who is taking a reasoned view over the issue and looking for the best advice. "
Ms Collins has not so far responded to calls from Radio New Zealand.
Justice Binnie's report is being reviewed by Robert Fisher QC. The minister said on Tuesday she expected to receive the review in the next day or so.