Treasurer Chris Bowen fears the federal coalition's long-awaited policy costings will amount to little more than a "dodgied-up spreadsheet".
Shadow treasurer Joe Hockey will on Thursday unveil the opposition's costings, which are expected to show a $6 billion improvement to the budget bottom line over the next four years.
Mr Hockey is expected to say that the improvement will be achieved through about $40 billion of savings and $34 billion worth of spending measures over the forward estimates.
But Mr Bowen doubts the savings will go anywhere near the "very big black hole" of cuts he says the coalition is planning.
"What I fear here is that on Thursday before the election, we're going to see a dodgied-up spreadsheet issued with no detail," the treasurer told ABC radio on Thursday.
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"And then after the election they're going to say 'Well, here are the cuts we're going to have to make based on our commission of audit'."
He says Australians are likely to remain in the dark about where those cuts will come from.
"They will not be releasing their detailed costings, they will not be releasing, from what I read, a detailed budget bottom line," Mr Bowen said.
"They're failing the basic test of an alternative government."
Finance Minister Penny Wong says Opposition Leader Tony Abbott has gone to "extraordinary lengths" to hide his planned cuts to public services.
"If you wrote about it in a novel, you'd think it was some sort of joke," she told ABC radio.
"(That) an opposition leader ahead in the polls would give some selected journalists some of his numbers 48 hours before the election, after the advertisement blackout has ended."
