WELLINGTON (Reuters) - New Zealand’s newly invigorated Labour Party has widened its lead over the governing National Party, further threatening its decade-long hold on power, a poll showed on Thursday, as the two party leaders exchanged jabs at their third debate in a week.

New Zealand's new opposition Labour party leader, Jacinda Ardern, speaks during an event held ahead of the national election at the Te Papa Museum in Wellington, New Zealand August 23, 2017. REUTERS/Ross Setford

National fell 2 points to 39 percent, while support for the opposition Labour Party was unchanged at 43 percent, the poll released on the website of the 1 News broadcaster showed.

New Zealand holds a general election on Sept. 23.

The poll still tipped the nationalist New Zealand First as a likely kingmaker, and showed the Green Party would only just make it into parliament.

Jacinda Ardern has almost single-handedly changed the chances of her Labour Party since taking over as leader last month, with her charisma and popularity offsetting some criticism over vague tax plans and tighter immigration policy.

National leader Bill English, who is pinning his bid on his government’s strong economic record, said he was not particularly worried about the poll results.

“On those numbers it would seem to me that a Labour/New Zealand First government would be the more likely outcome, but that all depends on a number of negotiations,” said Grant Duncan, associate professor at Massey University in Auckland.

“Based on these numbers, New Zealand First would be a key player for both Labour and National.”

The New Zealand dollar fell to the day’s low of $0.7173, having stood at $0.7207 shortly before the poll results were released.

The poll showed support for the New Zealand First Party rose 1 point to 9 percent, while support for the Green Party remained at 5 percent.

Duncan said the Greens were “perilously close” to the 5 percent voting threshold below which you do not get a seat in parliament.

Ardern reiterated that her first call would be to the Green Party, with which she has a working agreement, if she was in a position to form a coalition government after the vote.

The debate saw the party leaders trade jabs on taxes and housing, much as in their two previous encounters. It also touched on allegations this week by National that there is a NZ$11.7 billion hole in Labour’s fiscal plans - a claim rejected by Labour and one that has been refuted by economists, according to media.

“If you continue to maintain that then you’re maintaining a lie. That is misleading voters and it is wrong,” Ardern told English during the debate.

Support for Labour overtook that of National in a similar poll released a week ago.