Leader Judith Collins will finally launch her party's campaign today - but the lead-up was blighted by a torpedo from Labour's finance spokesman Grant Robertson revealing a $4 billion hole in National's economic plan.
The error means National's debt repayment plans have been changed, It now plans to have debt down to 36% of gross domestic product by 2034, instead of the 35% it promised on Friday.
Today Goldsmith apologised for the mistake, but said it did not mean the whole plan was flawed.
"This is an irritating mistake, we missed it and our external checker missed it as well - that's a mistake."
He said he had apologised to Collins.
"We make mistakes from time to time," he said, later adding that "I never claimed to be perfect".
The error would not affect National's plans to offer tax cuts, Goldsmith said.
This morning, Robertson accused National of not properly costing its policies.
The error is in regards to the savings National would make by cancelling its contributions to the NZ Super Fund.
National's economic plan said scrapping these contributions would save $19.1 billion - but Robertson said Treasury's estimates show the Government would have been contributing $15 billion over that time.
"National has used the wrong numbers," Robertson said.
Goldsmith has admitted to the error – saying the party had used numbers from the original Budget forecasts, rather than the ones from the Pre-Election Economic and Fiscal Update (Prefu).
"It changes the debt target in 15 years by 1 percent," Goldsmith said.
That 1% amounts to $4 billion.
Goldsmith went on to point out that National's error actually showed that Labour had "quietly cut the Super Fund to reduce debt, which they didn't announce and we missed".
"We are surprised, given their criticism of us for suspending payments to the Super Fund."
But speaking to media this afternoon, Robertson said this was not good enough.
"The mistake means they have $4 billion less of so-called 'savings' to pay for their ill-thought-through plan. This begs the question of whether there are other mistakes in their plan."
