Just under 300,000 special votes are still to be counted before the election result is official, prolonging the anxiety for some in marginal seats.

Candidates in just three electorates have a margin of fewer than 1000 votes -- Labour's Trevor Mallard in Hutt South, National's Nikki Kaye in Auckland Central and United Future's Peter Dunne in Ohariu.

In Hutt South, only 378 votes separate Labour frontrunner Mallard from National's Christopher Bishop.

Mr Bishop called Mr Mallard to congratulate him last night -- but not quite to concede until all the votes had been counted.

Advertisement

This afternoon Mr Mallard said: "I don't want to portray it as it all being over".

At 49 on National's party list, Mr Bishop will enter Parliament, regardless of the result in Hutt South.

But Mr Mallard will no longer be an MP if he loses the seat, having no place on Labour's list.

Mr Dunne, who is 930 votes ahead of Labour's Virginia Andersen in Ohariu, and Ms Kaye, who is leading Labour's Jacinda Ardern by 647 votes, are unlikely to be toppled in the official result.

But in Te Tai Tokerau, Mana's Hone Harawira has apparently still not conceded to Labour's Kelvin Davis, despite Mr Davis holding a 1,119 vote lead.

"I haven't heard from him at all," Mr Davis said this evening. "He rang last night to say that he wasn't going to concede, but that's 18 or so hours ago."

Political scientist Dr Bryce Edwards said Mr Harawira will probably benefit from special votes this year but it was unlikely the gap would close enough to change the result. "It does seem like he's grasping at a very thin chance."

Mr Harawira has not spoken to media today, and this evening did not return a message seeking comment.

Advertisement

Special votes could change party vote dynamics enough for parties to lose or gain MPs in the next fortnight.

"The Greens might yet go up," Dr Edwards said. "They normally benefit from special votes, and National often lose some special votes."

National leader John Key said today he didn't expect the special vote count to change National's 61-seat result.

But he predicted the official result may see may take one seat taken off Labour and handed to the Greens.

That would see Labour's Andrew Little out and the Green's Steffan Browning coming back in.

The highest number of special votes were cast in inner-city areas which host many students, itinerants and travellers. But the Electoral Commission says there's no way of knowing exactly which electorates these special votes will return to.

Special votes contain one envelope with the ballot paper, another with a declaration. These are separated, so votes stay confidential but declarations can be checked to verify the voter's enrolment status. Ballots are then sent to the voter's electorate for counting.

This year 293,130 special votes were cast -- nearly one-eighth of all votes. This included about 38,500 votes cast abroad.

The Commission says official results should be ready in a fortnight. Apart from special votes, all votes counted on election night are recounted.

The Commission hopes to release official results at 2pm on Saturday October 4.