The populist New Zealand First party is expected to hold the balance of power in the country's next parliament following the release of the final election tally.

Key points: New Zealand First leader Winston Peters says he'll make decision by October 12

New Zealand First leader Winston Peters says he'll make decision by October 12 Labour's Jacinda Ardern could still form government

Labour's Jacinda Ardern could still form government Peters describes NZ First as common sense party that doesn't like extremism

The ruling National Party won 44.4 per cent of the votes in the country's inconclusive September 23 election, while the opposition Labour Party took 36.9 per cent.

New Zealand First won 7.2 per cent of the votes, leaving it in a position to hold the balance of power in the formation of the next government.

New Zealand First leader Winston Peters has said he will make a decision which party to back to form a coalition government by October 12.

Mr Peters, a veteran New Zealand politician who has now held the balance of power three times, has in past elections formed coalition governments with both the National Party and Labour.

National leader and Prime Minister Bill English said the final election tally did not fundamentally change negotiations between his party and New Zealand First to form a coalition government.

"I don't think it weakens it significantly at all; the fundamentals haven't altered," Mr English told reporters in Queenstown in response to a question on his party's negotiation position.

Speaking to supporters in Auckland on election night, Mr English had said he would open talks with New Zealand First to "find common ground".

But Mr English's main challenger, Labour's Jacinda Ardern, could still form government.

"Sometimes MMP [New Zealand's mixed member proportional voting system] leaves us with an outcome that requires a little bit of extra work," she said on the night of the election.

The Green Party, which has a working agreement with Labour, took 6.3 per cent of the ballot.

Saturday's figures show National has 56 seats in the 120-seat parliament, Labour 46, New Zealand First nine and the Greens eight.

A Labour-Green coalition would have 54 seats, still short of a majority.

Sorry, this video has expired On the night of the election, both major leaders admitted there would be no clear winner.

New Zealand First's policies are thought to have more in common with those of Labour. Both want to curb immigration and adjust the role of the central bank, albeit in different ways. Some say Mr Peters could be swayed to go to National given it would be a straightforward coalition between two parties.

On election day, Mr Peters described New Zealand First as a "common sense party" that does not like "extremism".

"We believe in laws and policies that support the mass majority of New Zealand and not just a small elite who may have got control of the political system," he said.

Why do Kiwis support NZ First?

Associate Professor Grant Duncan from Massey University said nostalgia and economic nationalism played in favour of New Zealand First.

"It's because there's that nationalist and protectionist sentiment, but also I think Winston Peters' personality is an attraction to some people," he said.

"The New Zealand First supporters tend to be older, they tend to see immigration as a big issue, so a lot of the anti-immigration sentiment is concentrated in New Zealand First supporters.

"You get that economic nationalism and protectionism-based on a nostalgia."

ABC/Reuters