Jacinda Ardern elected Labour's deputy leader

Labour's caucus unanimously voted in Mt Albert MP Jacinda Ardern as the party's new deputy leader on Tuesday morning.

"Jacinda's a fierce advocate on the issues she has championed such as child well-being. She's worked hard during her time in Parliament and has the experience to be an excellent Deputy Leader," Labour leader Andrew Little says.

"We're going to make a great team on the campaign trail. Jacinda's a driven and dynamic campaigner who reaches a generation of New Zealanders neglected by this government."

"I believe our ideas will bring in the younger voters, in stark contrast to what we saw yesterday from the Government," Ms Ardern says.

Mr Little is not worried about being overshadowed by Ms Ardern's popularity.

Labour leader Andrew Little and deputy leader Jacinda Ardern (supplied)
Labour leader Andrew Little and deputy leader Jacinda Ardern (supplied)

"There's only one leader of the party, that's me, and we're a team", Mr Little says.

"I'm here to see Andrew Little elected as Prime Minister, nothing else" Ms Ardern says.

Last week Annette King announced she was stepping down from the role and will retire before the election in September.

Both Ms King and Labour leader Andrew Little nominated Ms Ardern to be take over shortly after.

"She has performed extremely well as a list MP and her resounding win in the Mt Albert by-election is further proof that she has what it takes to be my deputy," Mr Little said at the time.

Ms Ardern won 77 percent of the vote in the Mt Albert by-election, though turnout was low.

She is Labour's spokesperson for Justice, Arts, Culture and Heritage, Children, and Small Business, and was first elected to Parliament as a list MP at the 2008 election.