Revenue minister Peter Dunne has resigned from his ministerial portfolios after an investigation into how a top-secret report on the GCSB was leaked to media pointed to him.
Eighty-six emails were sent between Mr Dunne and Dominion Post reporter Andrea Vance in the lead up to the leak but Mr Dunne turned down requests to make them public.
Edited copies of the emails from Mr Dunne show 44 of them discussed the GCSB report, and he planned to meet with Ms Vance the day before she went public.
Former chief electoral officer David Henry has been conducting the investigation, and questioning those who were given a draft copy of the report.
"I remain of the view that I need full access to all 86 emails. In the absence of permission, I cannot take this matter any further," Mr Henry says.
"Mr Dunne has advised me that he has frequent contact with the reporter including communications by telephone, text, email and in person."
However, Mr Henry says Mr Dunne assured him he "did not provide the reporter with access to the Kitteridge report".
In a statement released a short time ago, Mr Dunne said he was "extremely concerned and upset" by the report's findings "in so far as they relate to me".
"While I did not leak the report, and challenge Fairfax to confirm that, some of my actions after I received an advance copy of the report were extremely unwise and lacked the judgement reasonably expected of a minister in such circumstances.
"I accept full responsibility for that."
Mr Henry's findings end more than a week of rumours and speculation that Mr Dunne was involved in the leak – despite him denying it and giving Prime Minister John Key his word.
The leaked report was compiled by Cabinet secretary Rebecca Kitteridge and highlighted a series of privacy blunders at the GCSB.
Mr Dunne, who is the leader of the one-man United Future party, has been the prime suspect since NZ First leader Winston Peters accused him of the leak on Wednesday last week.
The allegations were hotly denied by Mr Dunne, who called it a "scurrilous stunt" made under the protection of Parliamentary privilege by Mr Peters.
After the allegations were made, Mr Dunne was asked about his close Twitter relationship with Ms Vance.
"So what? I can see a whole lot of people here that I've engaged with on Twitter too," he said.
At the time, Mr Key called the allegations baseless and received "categorical assurance" from Mr Dunne that the leak didn't come from him.
However, today Mr Key said while he wanted to believe Mr Dunne, he could not "dismiss the possibility that he did leak the report".
"He's failed to comply with the investigation.
"The discussion themselves between the Minister and a reporter was inappropriate."
Mr Dunne this afternoon acknowledged he had not lived up to the "high professional standards" he had set himself as a minister.
“I have therefore concluded that I cannot continue to function effectively in these circumstances, given the lapses of judgement I have shown.
“The honourable course for me to follow now is to offer my resignation as a minister."
The official release of the Kitteridge report had to be brought forward because of the leak.
It found that 88 New Zealand residents or citizens could have been illegally spied on and it made numerous law and policy recommendations.
Mr Dunne's resignation does not affect the United Future Party's confidence and supply agreement with the National-led Government.