UPDATED 6.33pm: The National Party has waved the white flag in the upcoming Mt Albert byelection - announcing it will not stand a candidate.

Prime Minister Bill English has today confirmed a byelection will be held on Saturday February 25.

It is being held after David Shearer quit Parliament to heading the UN mission in South Sudan.

National campaign chair Steven Joyce denied the party was running scared after the Mt Roskill by-election result.

"If the Labour Party would stop losing their ex-leaders then we wouldn't have to have all these by-elections.  It is a very safe Labour seat and they just keep offering them up.

We are approaching the general election and we think we will just save our resources for that."

The Mt Roskill and Mt Albert by-elections were prompted by the resignations of Phil Goff and David Shearer respectively, both of whom led the party in the past.

The third ex-leader, David Cunliffe, has announced he will not stand again but will wait until six months before the general election to leave so it does not force a by-election in his New Lynn seat.

Labour MP Jacinda Ardern has confirmed she wants to be her party's candidate in the byelection. She has not been selected but is highly likely to be.

English said the Government was focussed on winning the 2017 general election.

“To achieve that goal, we don’t intend to participate in a byelection in the new year that is in a safe Labour seat.”

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

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

National got 14,360 party votes in the seat in 2014 - about 3,500 more than Labour but the Green Party got 8,000 party votes.

Shearer's resignation will take effect at the end of December and his new role as the head of the UN Mission in South Sudan will begin in January.

Jacinda Ardern, who is likely to be selected for Labour, said it was a strange call by National not to stand.

"Some people were predicting this but I didn't believe it. Regardless of the past record, in an inner city seat by-elections are an opportunity for parties to put their ideas forward. It seems very odd not to use that opportunity and just opt out altogether."

She said she had intended to run a grass roots campaign, talking to as many people as possibly and that would not change. "It's just there might not be as many billboards around, I guess."

She did not know if the Green Party intended to stand, having opted out of the Mt Roskill to reduce National's chances of an upset win there.

National stood its List MP Melissa Lee in the Mt Albert by-election in 2009 after Helen Clark left.

Then a rookie MP, she had blotted her copy book by saying the Waterview connection motorway would have the effect of diverting South Auckland criminals out of Mt Albert. She later apologised.

Ardern is a list MP and a win in Mt Albert means 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 Clark Gayford but had been intending to stand in Auckland Central for the third time prior to Shearer's resignation.

Ardern's 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.