By Tova O’Brien
The GCSB is so top secret that even its satellite dishes are hidden under opaque domes.
There are just two people it reports to: the Prime Minister, and Intelligence and Security Inspector-General Paul Neazor.
A retired judge, Mr Neazor ran the investigation into the agency's illegal spying on Kim Dotcom.
He admits, “they made a mistake”. But it's not just the one mistake they’ve made, contrary to what John Key suggested earlier this week.
In his annual report last year, Mr Neazor raised concerns three times about the GCSB operating outside of what was authorised.
In one case the authorisation needed to be limited, in another the execution of the authorisation was questioned, and an interception authority had expired in the third.
Green Party co-leader Russel Norman says it’s not surprising that the GCSB has stepped outside the law.
“The GCSB operates without any external scrutiny and in that situation it's only human nature that people start to view themselves as a law unto themselves,” he says.
Mr Key says Mr Neazor felt the GCSB’s mistakes were only minor.
“They were very minor process issues, they were resolved fully to his satisfaction and he never raised them with me,” he says.
And when 3 News raised those concerns with Mr Neazor he couldn't remember what they were, and instead compared his annual report to a poem by Robert Browning.
“Somebody asked Browning once what he meant by one of his poems and he said, ‘Only God and Browning knew what I meant and now only God knows,'” he says.
But Labour leader David Shearer isn’t satisfied the matter is resolved.
“I'm not confident about the accountabilities in this organisation and the accountabilities that run right up to the Prime Minister,” he says.
Labour wants a full inquiry, and so do the Greens. They’ve laid a complaint with police saying the GCSB illegally intercepted private communications.
It's the same charge camera man Bradley Ambrose faced during the ‘teapot tape’ saga.
3 News