National has called a $4 billion error in its fiscal election plan an "irritating mistake" - after accidentally basing part of its debt target figures on older information.
The party's finance spokesperson Paul Goldsmith has been forced to apologise to leader Judith Collins over the mistake and change its projected debt target from 35 per cent of GDP in 2034 to 36 per cent.
"As Grant Robertson helpfully pointed out, we based our fiscal plan on contributions to the Super Fund based on the (May) Budget figures," Goldsmith said.
"It turned out there was a slight change with (Wednesday's) Pre-Election Economic and Fiscal Update figures. The result of which is that instead of National's plan of getting out net debt as a country back to 35 per cent of GDP in 2034, we go to 36 per cent of GDP."
"This is an irritating mistake. We missed it. Our external checker missed it as well. And that's a mistake we made."
"I apologised to Judith Collins. We make mistakes from time to time."
Using May's figures meant National thought halting Super Fund contributions would save $19.1 billion, however the figures in the PREFU were updated to $15b instead.
It comes after Labour finance spokesperson Grant Robertson earlier today pointed out what he called "a basic error (that) has left a $4 billion gap".
"National has used the wrong numbers," he said. "The mistake means they have $4 billion less of so called 'savings' to pay for their ill thought-through plan."
Robertson accused the economic policy of being "desperate, irresponsible and unaffordable".
On Friday, the party launched its economic election promise of sweeping short term tax cuts and lowering the country's debt level to 35 per cent of GDP by 2034. It said part of how it would do that was by halting contribution to the Super Fund.
It was a step back from National's previous promise of 30 per cent in 10 years "given the scale in the PREFU", Goldsmith said at the time, adding it was "just not feasible and practical to get back to that level".
Today, Goldsmith said that was in contrast with the Government's plan of getting to 48 per cent of GDP by 2034.
On whether this had damaged the party's ability to balance the books, Goldsmith said that "the core of our plan works significantly well".
"What we have is that we're able to offer tax cuts to New Zealanders, we can continue to invest in public services and we can continue to pay down debt faster than the Labour Government, it's just going to be 36 per cent of GDP instead of 35."