The spymaster who initially cleared the Government Communications Security Bureau (GCSB) of illegally snooping on Kim Dotcom was also directly involved in seeking the suppression order signed by Bill English as Acting Prime Minister.
The Herald has learned former chief legal adviser Hugh Wolfensohn was involved in arranging the once-in-a-decade certificate which sought to bury the scandal.
The Prime Minister confirmed yesterday for the first time it was Mr Wolfensohn's advice that quelled GCSB and police fears they had illegally spied on Mr Dotcom and his co-accused Bram van der Kolk.
He told Parliament: "The best of the legal advice presented by Hugh Wolfensohn was that it was legal. As we now know, GCSB and Mr Wolfensohn were wrong."
Mr Wolfensohn no longer works at the bureau after being placed on "gardening leave". A spokesman for the GCSB said of Mr Wolfensohn's advice: "With hindsight, we know it wasn't right."
When GCSB's involvement began to emerge in August, the bureau tried to suppress its existence with a ministerial certificate. It needed the signature of the Prime Minister - and with Mr Key out of the country, it was signed by Mr English.
The Herald has confirmed Mr Wolfensohn was involved in arranging the certificate.
Mr Wolfensohn was a 25-year veteran of the bureau with key senior roles including as acting director during the illegal spying.
A month after the spying operation ended with the raid and arrests, concerns emerged the bureau had broken a law prohibiting spying on New Zealand residents. Mr Dotcom and Mr van der Kolk were residents at the time.
Mr Wolfensohn ruled the spying legal on February 27 last year.
Details of the GCSB's involvement have emerged in hundreds of pages of documents relating to the illegal spying obtained from court files by the Labour Party.
Included was a list showing the bureau received eight separate lots of legal advice in eight days before Mr Wolfensohn's eventual verdict the law was not broken.
Mr Robertson said the concerns, then advice dismissing fears and then the suppression certificate "had all the hallmarks of a cover-up".
"I find it inexplicable that having worked out it was unlawful that was changed by Wolfensohn. They all knew - and then worked themselves out of it."By David Fisher @@DFisherJourno Email David