Prime Minister Jacinda Ardern will step down on February 7.
A caucus vote will be held on Sunday for a new party leader and prime minister.
Ardern told a Napier press conference she would stay as an MP of Mt Albert until April to avoid the need for a byelection,
She had no plans beyond that as yet, and was looking forward to spending more time with her family.
Ardern said her team was ready to take the country forward and contest the next election.
“I am not leaving because I believe we can’t win the election but because I believe we can and will.”
She said there was no secret scandal behind her resignation. “I am human. We give as much as we can for as long as we can, and then it’s time. And for me, it’s time.
Ardern said she was not leaving because it was hard.
“I know when I have enough left in the tank to do it justice.”
“To Neve, mum is looking forward to being there when you start school next year. And to Clarke, let’s get married.”
Ardern also announced the next general election will be held on October 14.
Later Deputy Prime Minister Grant Roberston said he would not be standing for the leadership.