Justice Minister Amy Adams says the leak of a confidential report on David Bain's compensation will not change her approach to the matter, following concerns that the long-running process might have to start over.

The minister faced calls for an inquiry into the leak today, as MPs said it had derailed the compensation case.

Ms Adams insisted that it would not affect the way she was considering the report by Australian Judge Ian Callinan.

She expressed concern about "speculation" with regard to the report's contents, which the Herald revealed had found Mr Bain was not innocent beyond reasonable doubt.


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"It really is important that the commentary and analysis waits until people can see and read what Callinan has actually said," Ms Adams said.

But lawyers and MPs said the damage had already been done.

Former president of the Criminal Bar Association Gary Gotlieb said the leak could force yet another investigation.

He said there was a possibility the leaking of the report could prejudice Mr Bain's bid for compensation and predicted there would be people on the warpath hunting for whoever was responsible.

Labour and the Greens said the source of the leak needed to be found.

"We need to know how many people have had the report and who has had the report, including whether other ministers have it," Green Party co-leader Metiria Turei said today.

Labour's justice spokeswoman Jacinda Ardern wanted the Minister of Justice to launch an investigation.

"No one can afford to have this process derailed again," she said.

Act Party leader David Seymour said the leak had undermined New Zealand's justice system.

"The thought that you would leak a major report to try and soften up the public before making a formal decision is the stuff of banana republics," he said.

"I think people ... should ask themselves, whatever you think of David Bain, if it was you, would you want to face such a process of justice by politics rather than due process?"

Mr Seymour said Mr Bain should be compensated, at least for his legal costs.

Two reports have now been produced on Mr Bain's case for compensation, at a cost of more than $1 million.

The author of the first report, Canadian judge Ian Binnie, said today that the Government should take its lead from the court of public opinion and compensate Mr Bain for wrongful imprisonment.

"I don't think these reports are going to resolve the problem for the Government. I think what counts is the court of public opinion and there seems to be a strong majority in David Bain's favour and I think ultimately that will drive the result."

Otago University Law Professor Mark Henaghan said any matter of compensation was a political process where governments chose to compensate people if they thought it was politically appropriate.

Mr Bain was convicted of murdering his parents and three siblings in June 1994. He served 13 years in prison before the Privy Council quashed his convictions and he was acquitted in a retrial in 2009.