The Hamilton West by-election triggered by Gaurav Sharma's resignation will be held on Saturday, December 10.
"The by-election will be held on Saturday 10 December, with Writ Day being Wednesday 2 November," said Prime Minister Jacinda Ardern.
"The deadline for candidate nominations to be received will be noon Tuesday 8 November, and official results will be declared on Wednesday 21 December. The last day for the return of the Writ will be Tuesday 17 January 2023."
Ardern told reporters on Thursday the decision was based on advice from the Cabinet Office, informed by the Electoral Commission.
"That advice gave me a limited number of possible options, given, of course, the time of year we are in, public holidays and so on, and, of course, needing to take into account the final tally of votes being delivered before we move into significant end of year events."
The by-election has been prompted by Sharma, the now-independent Hamilton West MP who was kicked out of Labour in August, resigning his seat this week.
He claimed Labour was planning to use waka-jumping legislation to force him out of Parliament ahead of next year's general election. If he left Parliament within six months of the election, politicians could choose not to hold a by-election.
Sharma was concerned this would leave his Hamilton West constituents without an MP for months. By resigning this week, he triggered the by-election which he will run in.
However, Ardern has said there was no plan to use the waka-jumping legislation and has no idea what led Sharma to believe that.
On Thursday, she reiterated the by-election was a "complete waste of taxpayer money".
"I am still disappointed on behalf of taxpayers that we are having this by-election in the first place," she said.
Ardern on Wednesday began downplaying Labour's chances to win the seat. She said her party has been an "underdog" there lately.
"In recent elections, we've held it once out of five. That is the history of this seat. I let that record speak for itself for the type of contest it is likely to be," she said.
When it was pointed out by Newshub the electorate usually goes to the largest party - wasn't between 2008 and 2020 - Ardern said there have been boundary changes.
"I am saying in recent times we have been the underdog in that seat. I do think it would be a very robust and tough by-election," she said.
Labour, which won a majority of the vote at the 2020 election, has been trending down in recent polls and showing up as less popular than National.
Both parties are now readying for the campaign, but neither has chosen candidates yet.
Newshub revealed on Wednesday Roshan Nauhria, a wealthy businessman, is willing to back Sharma's by-election campaign.
"I will support him financially, 100 percent. Wholeheartedly… [it] doesn't matter the money, whatever he needs."
Sharma was officially expelled from the Labour Party on Thursday. President Claire Szabó said he had brought "the party into disrepute".
He was booted from the Labour caucus after making unfounded allegations of bullying towards MPs, accusing the Prime Minister of a cover-up and secretly recording his colleagues. He was then referred to Labour's governing body the New Zealand Council to decide whether he should be expelled from the wider party.
Following an investigation, the New Zealand Council met on Thursday morning to expel him effective immediately.
