The leader of New Zealand's main opposition party was ousted on Friday after opinion polls showed he was no match for the soaring popularity of Prime Minister Jacinda Ardern as the country heads toward a general election.

Simon Bridges was replaced by Todd Muller in an emergency caucus meeting of his centre-right National Party following a week of disastrous poll results.

Just 5% of New Zealanders supported Bridges, 43, as the country's leader in a poll published on Thursday, while support for the Nationals fell to the lowest in decades. The same poll revealed Ardern, 39, enjoyed the support of 63% of the electorate.

Ardern's popularity has shot higher in recent weeks with around 84% of New Zealanders approving of her government's handling of the coronavirus pandemic. Another poll showed Ardern had become New Zealand's most popular prime minister in a century and her centre-left Labour Party led coalition would be handed a huge victory at the Sept. 19 election.

Muller, 51, a largely unknown figure at the national level, had not been publicly perceived as a potential leader. Speaking to the media after the party ballot, he emphasised his strong ties to the rural farming community, the backbone of New Zealand's economy. Muller held roles at both dairy giant Fonterra and kiwifruit growers cooperative Zespri.

"I come from New Zealand communities that define this country," Muller said.

"The question sitting in front of all New Zealanders in the next 100 days is who actually has the best plan and the team to deliver it."

Muller said Ardern was "impressive" in her handling of the coronavirus crisis and his focus would be on the country's economic recovery, not criticising the current leader.

Nikki Kaye, 40, was elected as the Nationals' deputy leader, replacing Paula Bennett. Kaye has twice defeated Jacinda Ardern in previous electorate battles.