The new Coalition government has accused Labor of "cooking the books like never before" to hide a projected $4.5 billion hole in the New South Wales budget.

Premier Barry O'Farrell made the claim after briefings from Treasury yesterday.

"We all expected the finances to be worse than Labor had said, but frankly, it was a shock," Mr O'Farrell said.

"Treasury officials told the meeting that if the figures presented to us had been presented by the Labor treasurer to ratings agencies, we would have ended up with a review of our triple-A credit rating."

But Claire Curtin from Standard and Poor's says there is no threat to the state's credit rating at this stage.

"A significant proportion of the $4.5 billion number is both outside our outlook horizon and the forward estimates period," Ms Curtin said.

Head of Treasury Michael Schur was immediately asked to go on leave while an independent audit examines the state's finances.

The man expected to become the next state treasurer, Mike Baird, says it is clear Labor was hiding the true nature of the situation.

"However you spin this, state Labor have done every single trick in the book to try to present a case of every portfolio doing well," Mr Baird said.

"And the finances are no different. We found a $4.5 billion deficit when they were trying to tell everyone they were in the black."

But state Greens MP John Kaye says it is typical of Treasury to paint a bleak financial picture.

"The ink is barely dry on the Governor's signature and they're presented with a budget black hole.

"The budget black hole is nothing more than Treasury's desire to undermine public services and cut public investment in infrastructure."

Mr O'Farrell insists that, despite the projected shortfall, he will not wind back any of his election promises.

"The one pledge that I give the public is that we will deliver on the commitments given during the election campaign," Mr O'Farrell said.

Former state treasurer Eric Roozendaal did not respond to the ABC's calls this morning.