The new Finance Minister is accusing her Labour predecessor of finding "clever workarounds" to hide the true state of the government's finances.
Nicola Willis has also confirmed the coalition government will deliver its mini-budget on December 20.
Speaking from the Beehive, Willis said she was aware the previous government had committed to a number of long-term policies, but had only funded them for the short-term.
But having now looked under the hood, Willis says it's clear the Labour government upheld the "letter of the law, not its spirit."
Willis says she is still waiting for advice on how many "essential" initiatives would soon run out of funding.
But initial advice, she says, suggests billions of dollars over the forecast period could be needed to cover the cost of them.
Willis says this has prompted her to consider changes to the Public Finance Act.
Responding a short time ago, Labour's finance spokesperson Grant Robertson has rubbished the accusations.