The Government has rejected National's claim that 29 "fiscal time bombs" created by the coalition's new policies are waiting to go off.

Opposition finance spokesman Steven Joyce added them up in the Treasury's half- year economic and fiscal update, released last week, and said the number was unprecedented.

"These cover a huge range of election commitments that are yet to be included in the government accounts," he said.

He tackled Finance Minister Grant Robertson in Parliament on Tuesday over the list, and was told the Treasury had also identified a further 39 fiscal risks inherited from the previous government.

"The specific fiscal risks are Treasury's work, they're not political work," Robertson said.

"Treasury make their assessment of what they believe should go in there."

He said that of the 29 mentioned by Mr Joyce, 17 related to policy changes, four to departmental cost pressures, and four were cross-portfolio risks.

- NZ Newswire