Shadow treasurer Chris Bowen does not expect Scott Morrison's mid-year budget review will paint a pretty picture.
The treasurer will hand down the mid-year economic and fiscal outlook in Perth on Tuesday.
Economists expect the 2015/16 deficit could be between $37 billion and $40 billion, blowing out from the $35.1 billion forecast by former treasurer Joe Hockey in the May budget.
They anticipate this deterioration will occur across the four-year budget estimates, meaning that by 2018/19 the deficit could be as much as $20 billion rather that $6.9 billion previously estimated.
It will be a "damning picture indeed," Mr Bowen told Sky News on Sunday.
Economists expect this widening in the deficit will be the result of falling commodity prices, particularly iron ore, hurting company profits and tax revenue.
Mr Bowen said for Mr Morrison to continue to pretend that Australia does not have a revenue problem is neither a sustainable or constructive approach to the budget.
"For the treasurer to claim that he can return the budget to balance without dealing with revenue is just plain wrong," Mr Bowen said.
The deterioration will also reflect Australia's slower growth potential, which Treasury has already flagged will be 2.75 per cent rather than the three per cent forecast previously.
"The small surplus pencilled in for 2019/20 will remain elusive," Commonwealth Bank of Australia chief economist Michael Blythe predicted.
Since Mr Hockey made that 2019/20 surplus pledge, Mr Morrison has said he has no intention of repeating the mistakes of former Labor treasurer Wayne Swan - predicting budget surpluses only to look "foolish" when they are not met.
"The proof will be in the pudding," Mr Bowen said.
"We will be holding them to account for their previous commitments both in opposition and government (to a surplus), they can't just get a 'get out of jail free card'."
Mr Morrison has said he will need to find spending cuts to afford the $1.1 billion funding for the innovation plan announced last week, as well as other initiatives since May, such as reversing Labor's bank deposit tax, more road spending and the increased humanitarian refugee intake.
