The Labour Party is accusing the Government of fiddling the books in order to meet its target of a surplus in 2014/15.
The Government says Budget 2013 confirms the books will return to surplus in 2014/15 with forecasts showing that surplus is likely to be about $75 million.
Labour's revenue spokesperson David Cunliffe says the Government has had to resort to contortionist accounting tricks such as overcharging for ACC and raising petrol tax to scrape back into that surplus.
He says forecasts also show there will be a one-off spike in revenue of $600 million in 2014/15.
"If you add those up, you're between $2 billion and $3 billion of funny money assumptions that are required to get Government within a bull's roar of this supposed surplus. It's pretty meaningless really.
Mr Cunliffe says National has also forgotten to cost their minor tax credits to small business in the budget.
He says the manipulation of the numbers makes a mockery of the Fiscal Responsibility Act.