Labor has seized on shadow treasurer Joe Hockey's refusal to rule out coalition cuts to health and education.
On morning television on Friday, Mr Hockey was asked whether he'd rule out cuts to health and education if the coalition wins the September 7 election.
"I'm not going to give any on-the-run guarantees, I don't do that," he replied.
Labor says the "remarkable admission" gives a glimpse into the coalition's budget plans.
"Australian families have a lot to be worried about with the sort of slash and burn to education and health the coalition are destined to implement," a Labor campaign spokesperson said.
News that makes sense
Your trusted source for staying up-to-date with the world around you. Get free daily news updates and analysis, straight to your inbox.
"You can expect we'll have a lot more to say about this."
Mr Hockey also confirmed the coalition would wait until close to the end of the campaign to release its policy costings.
"Over the next three weeks, we'll roll out our agenda, as is appropriate, as has always happened in every election from both parties, and we'll reveal our costings then," he told the Seven Network's Sunrise program.
Mr Hockey's comments come after Opposition Leader Tony Abbott on Thursday indicated the coalition would wait until the final week of the campaign to release its costings.
Home Affairs Minister Jason Clare said the most important day of the campaign would be the day the Liberal party released its costings.
"That's judgment day. That's when the people of Australia will get a really clear idea of what they'll get with Kevin Rudd and what they get with Tony Abbott."
Former treasurer Peter Costello said it had become the standard practice for opposition parties not to release their costings until close to the election.
"I ran into it myself in government I think at the last election 2007, we got the Labor policies and about half the costings the day before," he told the Nine Network.
Mr Costello said holding back the costings was not a sign that bad news was to come.
He said also said he was against increasing the GST.
"I think you would increase it and they'd (the states) just waste the money anyway," he said.
