Labour claims National's campaign is "in meltdown" after a senior MP said a second election could be necessary if it couldn't secure a deal with ACT and New Zealand First.
Polls show National would need both parties to form a Government, despite the feud between ACT leader David Seymour and NZ First leader Winston Peters.
National's campaign chair Chris Bishop said they are concerned the inability to strike a deal with both minor parties could force Kiwis back to the voting booth.
"We will pick up the phone if we have to and try to make it work. But there is a real possibility of the necessity of a second election and it's a growing one, unless people cast a strong vote for change," he said, the New Zealand Herald reports.
Labour's finance spokesperson Grant Robertson said it's a sign National's campaign is "falling apart".
"They have introduced chaos into the last week of the campaign by saying they could force a second election rather than work with New Zealand First - after saying for weeks they would work with New Zealand First," he said in a statement on Sunday.
"A second election or a chaotic Government relying on Winston Peters would be another knock to our economy just when it's turning a corner and inflation is coming down.
"Christopher Luxon had the chance to rule out Winston Peters and avoid all this months ago. Chris Hipkins had the judgement to do so. Christopher Luxon didn't. This just shows the risk of Christopher Luxon's inexperience."
Labour leader Chris Hipkins slammed National for "threatening New Zealand with another election".
"I don't think that New Zealand needs another election," he said at a standup on Sunday.
"New Zealand First is not a recipe for stable Government - the fact that Christopher Luxon has breathed life into the New Zealand First campaign is a question for him."
Meanwhile Peters said there was no need for "scaremongering" remarks from Bishop.
"Suggesting the National Party would start scaremongering and threatening to ignore the will of the people on Election Day and ignore the need of our country to form a stable government would be highly troubling to voters," he said, according to the New Zealand Herald.
"It is telling voters National would instead enforce another costly election on the nation purely because of their own political expediency."
Luxon himself faced questioning over whether he could work with Peters on Sunday.
"It's up to the New Zealand people to decide, the voter is never wrong," he told media.
"And if they decide that they're putting them back in Parliament, then I will find a way to make that work as best as I possibly can."
