Internet businessman Kim Dotcom is considering suing the Government's spy agency over illegal surveillance.
The Independent Police Conduct Authority (IPCA) has found police were justified in not prosecuting any officers from the Government Communications Security Bureau (GCSB) for an illegal spying operation.
But Mr Dotcom told Checkpoint he did not agree with the IPCA's findings and he was 90 percent certain he would file a private prosecution against the GCSB for illegal spying.
Mr Dotcom said his legal team was sifting through all the documents and would give him a final analysis.
"So I've had preliminary discussions with my lawyers about this recent release finding that the police have acted appropriately in the GCSB criminal matter.
"We don't agree with the finding and I think that the only route that is left now is private prosecution."
In September 2012, the Greens asked police to investigate whether any GCSB agents had committed a criminal offence, after it was revealed the agency's surveillance operation against internet entrepreneur Kim Dotcom, had been carried out illegally.
The report by the then Secretary of the Cabinet Rebecca Kitteridge, which was released in March 2013, found 56 possible operations in total, involving 88 individuals, where the GCSB may have spied on New Zealanders illegally.
Greens co-leader Russel Norman subsequently wrote to the Commissioner of Police asking that his complaint be widened to cover all cases of possible illegal spying in the past decade.
Last September, he laid a complaint with the IPCA, claiming police had been negligent in not pursuing charges against GCSB agents, in relation to the Kim Dotcom operation.
That operation was illegal because under the law, the agency was not allowed to spy on permanent residents, which Mr Dotcom was.
When police announced they wouldn't be laying any charges, they said it was because, while the spy agency staff did technically break the law, they didn't have criminal intent.
That has now been backed by the IPCA, which found police were justified in relying upon an absence of criminal intent in their decision not to prosecute.
Green Party co-leader Russel Norman said he was disappointed with the IPCA's findings. He said in practice there was now a double standard in New Zealand's legal system.
"Individual citizens who breach the Crimes Act can and will be prosecuted but when (Prime Minister) John Key's spies breach the Crimes Act, even the same section of the Crimes Act, they won't be prosecuted."
Mr Norman said there were now no avenues left to pursue the matter.
"We've kind of been through the system now you know. We originally put the letter to the police saying you should prosecute those who broke the law - the police said no we're not going to and the IPCA backed up the police so basically the system is impenetrable to justice."
In relation to the other cases identified by Rebecca Kitteridge, the IPCA found that because those cases involved metadata, and the law at the time around the interception of metadata was unclear, the police decision not to investigate was justified.
Labour MP Grant Robertson said the lPCA's decision meant no one would be held responsible for the illegal spying operation, carried out on Kim Dotcom by the GCSB.
The decision would do nothing to restore public trust in the agency.
"Once again we don't have the level of accountability for the actions of the GCSB that New Zealanders want and that's been the problem throughout this process. The GCSB was involved in illegal spying. I'm not convinced the changes to the law have helped that - in facto the powers have expanded."
A police spokesperson said they considered the matter of whether or not they should have laid criminal charges against GCSB agents to be closed following the IPCA report.
The police did not intend to make any further comment.