John Key resigns: Allies, opponents react

John Key and Bill English have worked closely together for at least the past decade (Getty)
John Key and Bill English have worked closely together for at least the past decade (Getty)

Reaction to John Key's announcement in Parliament on Monday that he was stepping down as Prime Minister has been swift from both allies and opponents.

Deputy Prime Minister Bill English says Mr Key first told him in September that he was considering quitting the role, but that it was only confirmed to him this morning.

John Key resigns: Allies, opponents react

John Key and Bill English have worked closely together for at least the past decade (Getty)

Mr English was National's leader back in 2002, and is not ruling out gunning for the top job in Mr Key's absence, especially after the outgoing Prime Minister gave it his blessing.

"I would need to talk to members of the caucus and my family before considering it, but I certainly appreciate John Key's endorsement," Mr English said.

"I've had a master class every day from John Key about how to do politics, but in the end caucus will decide if my skills are better or different than them."

Mr English also poured cold water on speculation that Mr Key was ill, or that something else was behind him quitting as Prime Minister.

"There's nothing more to it, as he said in his press conference he's always tried to be direct and open with the NZ public.

"He came into this job on his own terms, different from the usual politics, and he's exiting on his own terms."

Cabinet will decide on who will take over from Mr Key at a Caucus meeting on December 12.

Response to the news from Mr Key's political allies - including his main rival Labour leader Andrew Little, has been mixed.

Normally fierce foes, Mr Little sent a tweet saying Mr Key had "served New Zealand generously and with dedication".

When asked whether Mr Key's absence will make next year's election easier, Mr Little said Labour would be ready "regardless".

In a news conference following the announcement, Mr Little said the party had already proven its ability to campaign.

"We've proved that at the weekend [with the Mt Roskill by-election], we proved it at the local government elections."

He says while it is a day to respect what Mr Key has done as Prime Minister, there are still "challenges" New Zealand faces which need to be addressed.

"Whenever the election is, we've got plans for the issues New Zealand needs to see fixed - housing, health, education, a rising crime rate - we are ready to go."

Former Prime Minister and Labour leader Helen Clark paid tribute to Mr Key in a tweet, saying he had advocated tirelessly for New Zealand on the world stage for the past eight years.

The Green Party has also paid tribute, saying "no matter your political allegiance, you have to respect someone who chooses to make the personal sacrifices required to be our country's Prime Minister".

Perhaps his most incessant critic, New Zealand First leader Winston Peters claimed the reasons for standing down "cannot be credible".

"The fact is that the economy is not in the healthy state that the Prime Minister has for so long claimed, and there are other issues which have caused this decision as well.

"Clearly the Prime Minister does not believe the superficial polls any longer."

Government partner and ACT leader David Seymour says Mr Key's legacy will be his "sound day-to-day" management.

"The challenge now is how do New Zealanders continue to get stable economically orthodox government in a post-Key era."