Steven Joyce is still backing his claim of a gaping fiscal hole in Labour's budget, despite numerous economists saying his $11.7 billion calculation is wrong.

The National finance spokesman told Three's The Project on Tuesday evening that nobody disagrees the opposition's numbers don't add up.

"Everybody's agreed there's a hole… the only debate is about how big it is and Labour are trying to fill it with their seven taxes," he said during a bickering match with Labour deputy finance spokesman David Clark.

But Mr Clark called that "rubbish".

"[Mr Joyce] has dug a big hole and he's thrown his credibility into it."

"Just hang on a second," Mr Joyce fired back. "Take a breath, there's still three days to go."

A Newshub-Reid research poll revealed 49 percent of New Zealanders don't believe Mr Joyce, with the other half either agreeing with him or not sure.