A supporter for David Bain has accused the Justice Minister of being in denial and keeping a report saying that Mr Bain should receive compensation secret.
Mr Bain is seeking a judicial review of the actions Judith Collins took after receiving a report from former Canadian Supreme Court judge Ian Binnie.
Mr Bain spent 13 years in prison, but was found not guilty in a retrial in 2009 of murdering five members of his family at their Dunedin home in June 1994.
In his report released late last year, Justice Binnie concluded that Mr Bain was innocent and suggest that he should receive compensation.
However a review of that report, commissioned by Ms Collins, criticised the judge's findings as legally flawed.
On Wednesday, Mr Bain filed a claim in the Auckland High Court, saying Judith Collins breached his right to natural justice, breached the Bill of Rights, acted in bad faith, abused her power and acted in a biased, unreasonable and pre-determined manner.
Joe Karam, a long-time advocate for David Bain, told Radio New Zealand's Checkpoint programme on Wednesday he believes Ms Collins has acted inappropriately.
"From the minute that that report arrived in (her) hands, suddenly there is denial, there is secrecy, there is running off to David Bain's adversaries for their view, and there is the commissioning of a report - not only to the exclusion of David Bain and his team, but without him even knowing it's going on."
Mr Karam said Mr Bain is reluctant to return to court, but has no confidence that his claim for compensation is being dealt with fairly.