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The counting so far has shown that Ardern's Labour Party are on course to win a landslide victory, returning Ardern to the top job for a second time.
Addressing a rally for her National Party, Collins congratulated her opponent, and thanked her supporters for their votes.
She said: "To PM Jacinda Ardern, who I have phoned before, congratulations on your result. It is, I believe, an outstanding result for Labour.
"It has been a tough campaign. New Zealand is in for a tough economic ride, and it is going to need better fiscal policy than we have so far seen.
"National will re-emerge from this loss a stronger, disciplined and more connected party.
"I promise you, the National Party will be a robust opposition.
"And I say to everybody, we will be back. Tonight is the start of the next campaign. Bring on 2023."
With just 70 percent of the votes counted, Labour had attained 46 percent of the votes, leading to the concession from the other parties.
It is thought that Ardern's leadership through the coronavirus pandemic, which has seen New Zealand return to almost normality while other countries continue to struggle, has been decisive in this election.
Ardern is expected to address her supporters at an event in Auckland shortly.
The opinion polls in the lead-up to the voting showed that Labour seemed to have a commanding lead, and so it played out on the day.
A record number of voters cast their ballots, accounting for nearly half of the population of New Zealanders on the electoral roll.
Ardern has become New Zealand's most popular Prime Minister of recent times, and one of the world's most respected politicians.
Despite the economic situation in the Pacific nation being fairly dire, Ardern's strong leadership and decision to close borders and enforce a full national lockdown led to New Zealand suffering just 25 deaths and less than 2,000 infections during the ongoing Covid-19 pandemic.
She's also increased benefits for impoverished New Zealanders, raised the minimum wage, increased parental leave, and banned future oil and gas exploration.
However, she has failed to deliver on other promises, such as affordable housing pledges, capital gain tax and reductions in child poverty.
On Friday night, she told Radio New Zealand: "I am not finished yet...I take some flattery in the idea that I would resolve a decades-long problem in three years but I can't."
She will now have at least three more years to get to work on the problems.
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