Jacinda Ardern says she's just taken on the worst job in politics but she'll bring "relentless positivity" to the party and next month's election campaign.
An hour after being named as the leader following the resignation of Andrew Little, Ms Ardern's message to Prime Minister Bill English is not to be complacent.
She'll take 72 hours to take stock of the party before bowling head on into "vibrant" campaigning alongside her new deputy, influential Maori caucus MP Kelvin Davis.
"There will be some core elements of our campaign that we absolutely stand by because they're the issue that New Zealanders have told us are important to them," she said.
"You'll see those as consistent things in our campaign but you'll also see Kelvin and [my] stamp on the campaign too."
Both new leaders were elected unanimously, following nominations by Mr Little and Grant Robertson respectively.
Despite his resignation from the leadership, Ms Ardern says Mr Little will remain a senior caucus member and minister in any government she leads.
1 NEWS NOW's live coverage for this event has now concluded. You can re-cap on the developments as they unfolded below:
Labour leader Andrew Little has announced he is stepping down as leader of the Labour Party after recent low poll results, with Jacinda Ardern elected as leader and Kelvin Davis taking the position as deputy.
2:25pm Jacinda Ardern has just had her first Parliamentary question time as the new Labour leader, where she confronted PM Bill English on the housing issue, challenging him to work with her on providing safe affordable housing for all New Zealander's. A statement which drew a chorus of applause from other members.
2:05pm Jacinda Ardern certainly isn't new to the TV game, we dug through the TVNZ archives to pull this footage of a young Ardern speaking about a scientific discovery she made as a sixth-form student.
1:45pm Looking over social media feeds, the leadership change looks to generally be getting a positive reaction. Could Labour's big gamble pay off come election time?
1:30pm Jacinda Ardern got off to a good start in her first press conference as leader today, drawing a chorus of laughs for this statement when asked if she has what it takes to be the leader of the Labour Party.
12.47pm NZ First leader Winston Peters has released a statement saying: "Jacinda and Kelvin will know that they have taken on a big job, some will say an insurmountable task, but we tender our congratulations."
He said Andrew Little "fought the good fight" but was a victim of transience of the polls.
12.30pm She finished the speech saying she wants Labour Party ideas to do the talking , and that she "wants to take stock for a bit".
12.28pm Jacinda Ardern's message to Prime Minister Bill English: "Don't be complacent".
12.24pm Jacinda Ardern would not say if Labour would keep their policy to move the new retirement age back to 65-years-old, saying she needed 72-hours to look at the policies.
Kelvin Davis said if the Maori Party is "still standing" after the election, "they'll have to up their game to work with us".
12.19pm Jacinda Ardern said they had the money and resources to continue campaigning with the leadership changes. She said it would be a "very, very vibrant campaign".
When asked if he would sit on the front bench, she said Andrew Little is likely to have a place there.
12.17pm Jacinda Ardern said the MOU with the Green Party still stands. She said the events today of Labour Party leadership changes were "extraordinary circumstances".
12.12pm Ms Ardern has said the Labour team is "determined and steadfast" leading up to the election, saying she is "incredibly lucky to call myself leader".
"I will use the next 72 hours… to reflect and take stock of the campaign plan. We will be positive, organised and ready."
She said she was a "young proposition" for the party, but the MPs who elected her had faith and "absolutely believe I am up to the job".
12.09pm New Labour Party leader Jacinda Ardern has begun her speech by thanking Andrew Little, saying he was "first and foremost loyal to Labour".
She said this morning's announcement was "not what anyone expected or wanted".
12.05pm As we wait for the new faces of the Labour Party to front the press, it is noted new leader Jacinda Ardern has the first question during Question Time today to Prime Minister Bill English.
From the parliamentary website: JACINDA ARDERN to the Prime Minister: Does he stand by his statement on the housing crisis that "I wouldn’t call it a crisis. We have strong demand, we have an uplift in prices – these are good problems to have actually?"
11.53am New Labour Party leadership team Jacinda Ardern and her deputy Kelvin Davis are to have their first media press conference beginning at 12pm. 1 NEWS NOW will have the footage livestreamed and on Facebook.
11.34am The Green Party have said their relationship with Labour "will continue to be sound now that Jacinda Ardern has assumed leadership of the Labour Party, and our congratulations goes out to her and new deputy leader, Kelvin Davis".
11.31am ACT leader David Seymour described Andrew Little standing down as requiring "enormous courage".
"I disagree with Andrew on many things, but he has more honesty and integrity than others on the Left. These qualities were on display today."
"What this means now is even more uncertainty over what a Labour-led government would look like," he said.
11.16am A press release from Jacinda Ardern said the decision was made at the Labour Party Caucus meeting today. Both Ms Ardern and Mr Davis ran unopposed.
11.12am Jacinda Ardern has been elected as the new Labour Party leader, unopposed. MP for Te Tai Tokerau Kelvin Davis has been elected as Deputy Leader.
10.43am An announcement regarding a new leader is expected to be made at midday today.
10.41am James Shaw says Andrew Little has done the honourable thing.
He says he feels "terrible" for Mr Little and enjoyed working with him.
He says he will work with Jacinda Ardern if she becomes leader.
He says a new leader could make a difference for the Labour Party when it comes to polling
The Greens co-leader is making an environmental announcement in Auckland and hasn't heard from Mr Little yet.
10.30am The Labour Party caucus meeting is scheduled to start now, which will see Mr Little officially no longer Labour Party leader.
10.26am In his speech, Mr Little said: "In the end the only thing that matters is that we can run a good campaign, unclutter by polls and narratives about polls and leadership."
"We gotta get focused on the things that matter."
"We have proven we have a depth of talen in the party, we have a determination to get out there, campaign out of our skins, and win."
10.18am He said he still remains "utterly determained" to win the 2017 election with Labour, but "it became pretty clear the story around those polls was building a narrative day after day".
10.14am Andrew Little said the party would be "better served by a new leader who can bring a fresh face and a fresh voice to this vital campaign".
He said he has not seen the list of potential candidates for leadership but he "suspects Jacinda will be nominated or will step up".
10.09am In a statement from Mr Little, he said it was "a sad decision".
"I have been privileged to have led a united, talented team of Labour MPs, proud to have progressed the values and issues that New Zealanders care about and proud to stand with working New Zealanders."
10.05am Mr Little said he has just confirmed to the Labour caucus he is stepping down. "There is no question the poll results that came out last week... were disturbing and very, very disappointing.
"As leader, you have to take responsibility, and I have, and I do."
10am Labour Leader Andrew Little announces he is stepping down.
9.57am Earlier this morning on TVNZ1's Breakfast, former Labour Party President Mike Williams said the argument for a need for a "circuit breaker" to increase poll results has prevailed.
He said the party could "absolutely" turn itself around in the eight weeks prior to the upcoming election.
9.45am Andrew Little has announced he will be fronting media at 10am this morning. Stay tuned with 1 NEWS NOW for live streaming.
9.30am Jacinda Ardern, who has been predicted to take over as leader, told 1 NEWS "Andrew's had my support the entire time".