Dunne quits as minister - is Key party over?

United Future leader Peter Dunne has quit as a minister, further heightening the possibility of an early election.

But in an offhand response Prime Minister John Key says there is no need for a snap election.

"If I went  to the Governor Ggeneral this afternoon and said I wanted a snap election he would probably tell me to go away. There's just no grounds for it."

Finance minister Bill English will take control of the Revenue portfolio. Mr Dunne will remain as an MP and support the government on supply.

The Ohariu MP's vote has been crucial to the government on a number of issues, including the asset sales legislation that passed by one vote.

Mr Key says he gave Mr Dunne the choice of fully meeting the requirements of the inquiry into who leaked details of the GCSB report into surveillance of Kim Dotcom, or resignation. Mr Dunne chose the latter.

The report says Mr Dunne refused to allow the head of the inquiry, David Henry, to view the 86 emails exchanged between him and the Dominion Post reporter, Andrea Vance, over the period the material was leaked, between March 27 and April 9.

Mr Dunne showed him an edited text of emails, of which 14 were partly and four were completely deleted.

The emails also show Mr Dunne planned to meet Ms Vance on April 8, the day before the story appeared, and that Ms Vance was waiting to meet Mr Dunne that day.

Security records also show Mr Dunne left his office at 11:35am that day and returned at 12:27pm.

Mr Dunne told the inquiry he did not in fact meet Ms Vance that day.

"He also advised me he did not give the reporter  access to the... report."

Mr Key says he wants to believe Mr Dunne when asked if he thought Mr Dunne had leaked the GCSB information.

"I am completely at a loss to explain this."

At a press conference, Mr Dunne at one point said he was following his principles in not releasing private correspondence between himself and Ms Vance; at another he offered "I cannot rationally explain what I did."

Labour and the Greens have called for a police investigation into whether Mr Dunne leaked the appendix to the GCSB report, which has never been made public (unlike the body of the report, which was always scheduled for public release).