Prime Minister Kevin Rudd says Labor set its planned return to a budget surplus using Treasury numbers, indicating the government doesn't think the next update will be much different.
The departments of Treasury and Finance will on Tuesday release the Pre-election Economic and Fiscal Outlook (PEFO) - an independent assessment of the budget and the economy.
Mr Rudd was asked if trust in Labor's budget plans could be undermined if the PEFO numbers were different to those in the government's economic update released on August 2.
"We work with the data we are given," he told reporters in Sydney on Monday.
"The Treasury provides its best analysis of revenue projections, we act with on that.
"The challenge for our opponents, 24 hours from PEFO, is to level with the Australian people."
Shadow treasurer Joe Hockey said the opposition won't rush its response.
Meanwhile, Mr Rudd continued to pressure Mr Abbott on the GST, even though the opposition leader has rejected suggestions the coalition plans to raise the rate of the consumption tax or broaden its base.
Under rules governing changes to the GST, all states and territories, and both tiers of federal government, have to agree.
But Mr Rudd said if any future Australian government wanted to change the legislation it could put a bill before parliament.
"It's as simple as that," he added.
"His core argument that there isn't a problem because everyone will have to agree is actually a false argument."
The coalition does plan a review of the taxation system if it wins government on September 7.
The review could include the GST.
The coalition has said it would take any such proposal to the next federal election.
