Prime Minister John Key says two of his top ministers would make fine future leaders but he hopes a decision on his successor would be "a long way into the future".

Mr Key and his deputy Bill English discussed the National Party's succession plans in an interview with TVNZ's Q+A programme today.

Mr Key said there was no succession agreement between them.

"And the truth is that we've got a broad caucus and there's lot of people you could point to that actually could come through, depending on the timing. I think there's a range of people, both on the front bench and people who are emerging."


Asked who he would choose out of senior ministers Steven Joyce and Judith Collins, Mr Key said that would not be his decision because he would not be part of the party caucus.

"The caucus would be making that decision, and if they were doing a coup, they wouldn't be coming to consult me on it, so we're not too worried about that," he joked.

"I personally think both of them would make fine leaders and fine prime ministers, but there's others as well, and it will depend on the timing.

"Hopefully it's going to be a long way into the future, and that will bring other people into play as well."

Mr Key said National was in a "healthy position".

"We've worked really hard I think, in Cabinet, to have a range of people at different levels. We have rotated and brought people in."

The party had learned a lesson from former Prime Minister Helen Clark and her deputy Michael Cullen.

"They were extremely dominant and ran a tight ship from the Labour Party's perspective, but when they left after the 2008 election, there's been a massive hole that I'm not quite sure they've even managed to fill yet."


Labour has had three leaders since Ms Clark stepped down at the 2008 election - Phil Goff, David Shearer and current leader David Cunliffe.

Mr Key said he did not have "a plan B" if National lost the election.

"I'm totally focussed on winning the election. But I've been reasonably up-front with people saying that eventually, if you lose an election, generally there's a change of leader.

"I don't think it's actually healthy to get in the way of the next leader, and most prime ministers that have lost elections haven't stayed around long-long-term.

"But in the end, I hope we win and I hope we get to stay there because it's very much unfinished business."

Mr English said he would not expect to take on Mr Key's role.


"I wouldn't be expecting to do that, but in any case those are matters for a caucus and the wider party."

Asked if he would stick around if National lose next year's election, he said: "To be honest I haven't really thought about that - I suppose, when you're close in the election."