WELLINGTON (Reuters) - Neither major New Zealand political party leader on Monday would rule out appointing nationalist New Zealand First head Winston Peters as deputy prime minister as poll averages showed a neck-and-neck race for a Sept. 23 election.

FILE PHOTO: Jacinda Ardern (C), New Zealand's new opposition Labour leader, speaks to the press alongside members of her party after Andrew Little stepped down in Wellington, New Zealand, August 1, 2017. REUTERS/Charlotte Greenfield

Labour’s Jacinda Ardern and Prime Minister and National Party leader Bill English faced off in a fiery televised election debate, the same day tightening poll averages suggested each would still need New Zealand First to form a government.

The leaders traded jabs as Ardern accused the center-right National Party of ignoring a housing crisis in its nine years in power, while English criticized his 37-year-old, center-left opponent of putting ideals over concrete projects.

“You can’t replace a plan with a vision,” English told Ardern.

Labour has argued that New Zealand’s economic growth rate, among the fastest in the developed world, on the National Party’s watch, has masked growing inequality and strains on infrastructure.

Labour also says people are not seeing the benefits of growth, with wages still lagging behind living costs.

“People ... feel like they are going backwards. And that’s because they are. An economy should be about people,” Ardern said.

Both party leaders said they would not make Peters, who would like to slash immigration and increase the central bank’s ability to intervene in the currency, finance minister in their governments.

Labour’s soaring support since charismatic Ardern took over as leader on Aug. 1 may put it in a position to form a government without having to rely on the controversial nationalist party if its momentum is sustained.

National, however, looks as if it would likely still be heavily reliant on the New Zealand First Party, whose support is also waning.

Although both major parties are open to forming a coalition with the populist party, Peters has not said which one he would throw his lot in with.

KINGMAKER?

Labour’s average level of support in opinion polls rose to 39.8 percent, and the Greens’ average was 6.2 percent, figures released by media on Monday showed, putting the two parties, which share a working agreement, comfortably ahead of National’s 41.6 percent.

A party, or combination of parties, needs 61 of Parliament’s 120 members in order to form a government in New Zealand’s German-style proportional representation system.

The averages suggest Labour and the Green Party would garner 57 seats, compared with National’s 51.

“If National happen to drop a bit further, they won’t have any chance of forming a government because they don’t have as many coalition options as Labour,” said Bryce Edwards, a political analyst at Victoria University in Wellington.

Only weeks ago, outspoken Peters was expected to be the kingmaker in the formation of government after the vote.

But a controversy over mistaken overpayment of superannuation to Peters has hurt his support, while voters have also been drawn to the newly invigorated Labour party.

Although the average of polls shows New Zealand First remains decisive in the formation of the next government, the situation could change if its loss of momentum continues, analysts say.

New Zealand First’s average fell to 8 percent, down from 9.1 percent on Friday.

“Certainly New Zealand First, if they are somewhere in the 5 percent to 7 percent range, there will be a good chance of them no longer being a kingmaker after the election,” Edwards added.

Support for the party fell to 6.6 percent in a poll released on Sunday, following a drop to 8 percent in another poll last week. Both polls were used to calculate Monday’s average.