The two main contenders for the Mt Albert byelection have been revealed - with one promising a different style of political contest.

Labour MP Jacinda Ardern and Green MP Julie Anne Genter were tonight confirmed as candidates by their respective parties.

I've just been selected to stand in Mt Albert for the by-election! Looking forward to a positive campaign with excellent Green solutions.

— Julie Anne Genter (@JulieAnneGenter) January 12, 2017

National is not standing a candidate in the February 25 byelection, which is being held after David Shearer quit Parliament to head the UN mission in South Sudan.

Genter, her party's transport, health and Auckland issues spokeswoman, said National's absence meant the byelection was an opportunity to "show how politics can be done differently - respectfully, positively, and collaboratively".

"I'm really keen for us to demonstrate that it is possible to do politics differently. That it doesn't have to be a war or people yelling at each other."

Genter said policy debate would hopefully be at the fore - her key issues are housing affordability, transport, and health services.

Asked if she would offer any criticism of Ardern or Labour policies, she said it wasn't necessary to be negative.

"Jacinda - if she is the Labour candidate - is a fantastic MP, I really respect her and look forward to working with her in Government."

Ardern told the Herald she was excited about the chance to focus on policy in the byelection, which would "be very positive".

"Byelections are an opportunity for political parties to present their vision... the surprise to me hasn't been that the Greens are running, it has been that National isn't running.

"I'll be out there talking about all the reasons why I would love to be the candidate for Mt Albert, but demonstrating that, at the same time, Labour and Greens have a relationship that means we will be able to work effectively in Government."

Genter lives in Mt Eden and stood in Epsom in the 2014 general election. New Green MP Barry Coates is expected to stand in Epsom this year.

Genter said she used to live within the Mt Albert electorate and knew the area well. The Green MP conceded Ardern was the favourite but said she looked forward to the campaign and debating "the finer points" of the policy issues.

There are a large number of Green voters in the Auckland electorate - 22 per cent of voters in Mt Albert gave their party vote to the Greens in 2014, about double the national result.

Shearer won Mt Albert in 2014 with a majority of 10,656 votes.

National got 14,360 party votes in the seat in 2014, ahead of Labour on 10,823 and the Green Party at 8005.

In announcing the decision not to stand a candidate, Prime Minister Bill English said the seat was a safe one for Labour and his party wanted to focus on the general election.

That decision comes after National candidate Parmjeet Parmar lost heavily to Labour's Michael Wood in the Mt Roskill byelection in December.

The Green Party did not stand in that byelection, a decision reached after Labour and the Greens signed a Memorandum of Understanding, with the aim of changing the Government.

Ardern is a list MP and her probable victory will mean another Labour List MP will come into Parliament. Next on the list are Maryan Street and Moana Mackey, but Labour leader Andrew Little is understood to be keen to get Raymond Huo in to provide Chinese representation.

Ardern recently moved into Mt Albert with her partner Clarke Gayford but had been intending to stand in Auckland Central for the third time prior to Shearer's resignation.

Her shift to Mt Albert will open up the candidacy for Auckland Central, which Ardern was hoping to win from National's Nikki Kaye on her third attempt.

Meanwhile, nominations to be Labour's candidate in New Lynn also closed tonight.

Massey University senior lecturer Dr Deborah Russell is seeking the nomination for the safe Labour seat, vacated by former party leader David Cunliffe, who is retiring from politics.

- NZ Herald