Labour leader Andrew Little said Labour is in talks with those next on its party list should Jacinda Ardern be selected and win the Mt Albert electorate after David Shearer's departure.
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. That is likely to mean a byelection in Mt Albert and Ardern, a List MP, said she would put her name up for the seat.
Should she win the seat another Labour List MP will come into Parliament. Next on the list are Maryan Street and Moana Mackey, but Little is understood to be keen to get Raymond Huo in to provide Chinese representation.
Little said talks were taking place and one had indicated they were not interested in returning, understood to be Mackey. He would not say whether Maryan Street had been offered progress on euthanasia reform in return for stepping aside.
"I've heard the suggestion. I haven't had any further discussions and a lot of things remain a possibility."
He said he supported Ardern's bid for Mt Albert but expected others to put their names in as well.
"No doubt there will be a long queue because there was last time we had a selection in Mt Albert, but she will be a fantastic MP for Mt Albert and we'll see who else wants to join the sing-song."
He said Ardern had profile and experience which were talents she would bring to a selection contest.
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.
Little said Ardern's inability to win that seat should not count against her.
"If you look at what she achieved in elections where the tide was going against us she's gone very very well."
Little said Labour had a "growing black book" of potential candidates.
Little also paid tribute to David Shearer, saying he was "the best foreign affairs minister we'll never have".
"And as a support to me and a person who's given advice to me, he will be a source of wisdom that I won't have access to, easily anyway."
Ardern seeks Mt Albert seat
Labour MP Jacinda Ardern has put up her hand to stand for Labour in Mt Albert in the likely byelection prompted by incumbent David Shearer's departure.
Labour is almost certain to select Ardern for the seat, which Labour has held since it was created in 1946 and was former Prime Minister Helen Clark's stronghold between 1981 and her departure in 2009.
A byelection is likely early in the new year unless Prime Minister Bill English calls an early midwinter election, which he has indicated is unlikely.
Until Shearer's resignation, Ardern had expected to stand again in the marginal Auckland Central for the third time after losing to National's Nikki Kaye in 2011 and 2014. Kaye has a 700-vote majority - the slimmest in New Zealand. Kaye is still on leave being treated for breast cancer but has confirmed she will stand again.
Asked if Ardern was effectively conceding defeat to Kaye in Auckland Central, Ardern said "everyone knows I lost twice - the results are pretty clear. But no, it's not a concession. I still genuinely believe Auckland Central can be won and I intend to work closely with whoever is the new candidate if I get selected [for Mt Albert]."
Ardern said the seat had a good pedigree, but she had not yet been in touch with Clark.
"I would love to get her advice because it was her home and her seat for so long. There's no doubt the seat has a wonderful history. I guess that's a happy coincidence of that seat."
She had recently moved into the Mt Albert electorate, but said the decision to switch her candidacy to Mt Albert had been a genuine dilemma because she had worked in Auckland Central for eight years and built up a good team.
The Green Party polls strongly in Auckland Central and it was in a mix of electorates in which a deal was being considered to help ensure Labour won the seat back.
Boundary changes before the 2014 election meant parts of the old Auckland Central were now in Mt Albert, including Grey Lynn, Arch Hill and Westmere.
Shearer won Mt Albert in a byelection in 2009 after Clark's resignation to head the UN Development Programme in New York.