National Leader Simon Bridges is accusing the Government of "screwing up the economy," after new Treasury figures revealed the books would be going into deficit next year.
He is also critical of the Government's economic management, after new GDP numbers showed the economy is growing slower than has been expected.
At the Half Yearly Economic and Fiscal Update (HYEFU) this morning, Treasury revealed next year there will be $900 million deficit – down from an expected $1.3 billion surplus.
• Government plans on borrowing likely billions to fund a 'significant' infrastructure spending spree
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• Crown accounts: Government's $7.5b surplus is the biggest since 2008 GFC
• The Government will borrow an extra $19b; and announced $12b of new spending on infrastructure projects
But Treasury also expects $12 billion worth of surpluses over the next four years.
"Labour is screwing up the economy in two short years," Bridges told reporters this afternoon.
He said they had gone from surpluses "as far as the eye could see to going into the red".
This was "unbelievable," he said.
He was also critical of the Government's borrowing plan.
It was also revealed this morning that the Government is expected to borrow an extra $19 billion to help pay for an extra $12 billion worth of infrastructure spending.
"The Government is putting [spending] on your, your children's, your grandchildren's credit cards," Bridges said.
But, responding to questions from Bridges in the House this afternoon, Prime Minister Jacinda Ardern defended the Government's economic record and the new spending.
"With New Zealand's low debt and borrowing costs, this is the right time to invest to futureproof New Zealand after nine years of neglected infrastructure under the National government."
When quizzed about the deficit, Ardern pointed out that much of it was down to a changed ACC forecasts and the global downturn.
But, she said the same Treasury forecasts show that in the years after next, the Government is expected to be back in surplus.
Meanwhile, the reaction from economists has been mixed.
"Although this new investment is large, the Government could have made a much larger investment announcement," according to Infometrics economist Brad Olsen.
CTU Economist and Policy Director Bill Rosenberg called the new spending greatly needed.
"After a long period of neglect we have fallen well behind and this investment is significant. It makes sense given government debt levels are low and its borrowing is currently very cheap."
ANZ, whose chief economist Sharon Zollner has in the past advocated for more spending on infrastructure, said today that the new spending would help growth.
"However, given the delays typical with infrastructure spending, we doubt they'll be able to implement this as quickly as they hope.
"We await further announcements regarding the specific projects to be funded."