The Electoral Commission is rechecking all voting results after a data entry error wrongly saw two fringe parties gain hundreds of votes at three voting booths.
Two voting places in Port Waikato, and one in Christchurch electorate Ilam, saw hundreds of votes wrongly allocated to the wrong parties.
The Leighton Baker Party and the New Conservatives were beneficiaries of the errors.
Most of the wrongly allocated votes should have gone to the National Party, and some to Labour, Greens, NZ First, Te Pāti Māori and some of the small parties that did not reach Parliament.
Chief electoral officer Karl Le Quesne explained to Morning Report how the mistake happened.
"When the official count was done in these two electorates, they were checked and signed off as accurate and then they were entered into our electoral management system. And at that stage it looks like in each case, either some zero counts were missed out or added in where they shouldn't be.
"And then all the rest of the results were misallocated, and it really just reflected which parties got the misallocated votes with the alphabetical order they were listed down on the sheet. So that's how it happened.
"Now, we run a quality assurance process program across all of the results once they've been entered and it does pick these sorts of things up. But unfortunately, we missed these three."
The error was first picked up by the New Zealand Herald.
"We're really disappointed we missed these and we want to apologise for that," Le Quesne said.
"The board that oversees the commission is going to get a full independent review done of their quality assurance processes just to see where we need to make some improvements and avoid this ever happening again."
Le Quesne said the mistake - caused by human error - did not affect the overall election results.
He said the returning officers in the electorates where the mistakes happened were "obviously incredibly disappointed", but there was no evidence of anything suspicious.
"We've looked at the patterns across the three that we've identified and they don't favour any particular party or political views… The numbers were put in the wrong sequence and that's what it is."
Of the approximately 10,000 booths, the three discovered by the Herald were the only ones with party vote anomalies found.
"We're just completing the candidate vote counts today," Le Quesne said. "We've got a couple we're looking into, but again, we're not seeing anything that would change any of the results, either at an electorate level or the party vote."
He did not say which candidates or electorates might be affected.
"If we do find anything, we will make that public… they're not in any seats where there's a close margin."
Any candidates seeking a full recount needed to have their applications in by 5pm on Wednesday.
Baker, who saw his party fall from third-to-last to second-to-last in the party vote, was philosophical about the vote reallocation.
"It shows that although systems can have faults, at least there are enough checks and balances to pick them up," he told 1News.
National Party leader Christopher Luxon said the matter should be looked at along with other concerns he had already raised.
"As I've already said, there are a lot of good questions to be asked and answered after a government is formed about the Electoral Commission and what we learnt from the election. I'd expect this to form part of that."
The Justice select committee holds an inquiry into the general election every three years, where the Commission gives evidence and answers questions from MPs, who then make recommendations.
In 2020, the committee made nine recommendations, six of which were accepted with the other three referred to the separate Independent Electoral Review.