Kelvin Davis happy to give up Deputy PM role

Kelvin Davis says he'll give up the Deputy Prime Minister role if that's what it takes for Labour to lead the next Government.

"I'm not going to get in the way of Jacinda being Prime Minister," the Labour deputy leader told The Nation on Saturday.

Recent polling suggests Labour will need the help of at least one, probably two other parties to form a Government after the September 23 election.

With both the Greens and NZ First polling above 10 percent, there's a good chance Winston Peters or James Shaw might push for the Deputy Prime Minister role.

Mr Davis' willingness to give up the job echoes a promise Labour leader Jacinda Ardern made just two weeks ago, when she was deputy to Andrew Little.

Ms Ardern said then there was no 'plan B' if Mr Little wasn't Prime Minister. Turns out she was plan B, after he conceded the leadership to her on Tuesday morning.

She said at the time, she truly didn't want to be Prime Minister - but realised on Tuesday Labour appeared to be in an irreversible slide under Mr Little.

"Andrew made a massive, selfless call on behalf of the party," Ms Ardern told the Nation on Saturday.

"I had goals and ambitions as a politician that I believed I could have achieved as a minister - but of course, that required us to be in Government."

She declined to say whether she'd remain on as leader if Labour lost the election, but Mr Davis seemed keen.

"We'll back her right through into 2035 when she's probably had enough of being Prime Minister."