Last week National's finance spokesperson Steven Joyce claimed Labour's fiscal plan had an $11.7b hole. That claim, denied by Labour's finance spokesman Grant Robertson, has been debunked by virtually all economists who've been asked about it.
In the debate, Mr Joyce said there were "lots of people" who backed his initial claim, but declined to name anyone.
Mr Joyce defended his claim and said Labour had now adjusted its figures.
"They're saying they'll run zero budgets - which is entirely unbelievable - and as a result there's a bunch of people who say it could be made to add up if they run zero [budgets]."
Mr Robertson said it was a disgraceful allegation that "not one person in New Zealand" has backed up.
"You have damaged democracy by what you have done. This is fake news."