New Zealand kingmaker Winston Peters says he will form a coalition with Labour and the Greens, handing Jacinda Ardern the prime ministership.

The 37-year-old leader of the Labour Party beat out the National’s Bill English, 55, who had been prime minister since December 2016.

NZ First leader Mr Peters, whose minority party held the balance of power after elections in late September, announced his choice on Thursday afternoon (AEDT).

Mr Peters said issues of economic inequality, such as access to affordable housing, were the key issues that swayed his party’s decision.

“There are far too many people living in degraded and poor conditions in this country.”

The coalition deal was conditional on the building of 10,000 affordable homes annually, Mr Peters said.

Mr Peters said the Labour leader’s campaigning skills also helped persuade him, saying she displayed “extraordinary talent”.

Prime Minister elect Jacinda Ardern speaks during a Labour Party announcement. Photo: Getty

Ms Ardern addressed the media shortly after the decision, thanking Mr English for his service as New Zealand prime minister and finance minister.

She said Mr English has conceded that coalition talks have now concluded.

“This is an exciting day. We aspire to be a government for all New Zealanders and one that will seize the opportunity to build a fairer, better New Zealand,” Ms Ardern said.

Ms Ardern also announced the Labour caucus will meet on Friday afternoon to elect cabinet positions.

She said New Zealand First will hold four cabinet positions and one junior ministerial role.

New Zealand First holds the balance of power with nine seats, a Labour-Green bloc controls 54 seats, and the National Party 56 seats.

The Greens have also been offered ministerial portfolios but Ms Ardern would not be drawn on what roles they could be.

Mr English said he was proud to leave New Zealand “in great shape … a more confident country with more aspiration”.

Earlier, Mr Peters took his time to reveal his decision, frustrating many on Twitter who had waited weeks for the announcement.

https://twitter.com/richjamesuk/status/920891118471979008

Is he getting paid by the hour or something? #nzpol

— Andrew (@andkiw) October 19, 2017

Winston makes us wait by explaining why he made us wait so long #nzpol

— Harry Chapman (@howdystrangr) October 19, 2017

Ms Ardern has long been recognised for her youthful and progressive injection into New Zealand politics, since first joining the Labour Party at the age of 17.

Born in Hamilton and raised in a Mormon household, Ms Ardern reportedly left the faith in her early 20s due to its anti-homosexual stance.

Ms Ardern studied politics and public relations at Waikato University and worked for Mayor of Auckland Phil Goff and former prime minister Helen Clark.

She later spent three years in London as a policy adviser in the UK Cabinet Office and worked for former British PM Tony Blair before returning to New Zealand to campaign full-time in the 2008 election.

She was first elected as an MP in Mount Albert, where she lives with her partner, broadcaster Clarke Gayford.