The coalition must come clean on its plans for the low income superannuation contribution, Employment Minister Bill Shorten says.
Mr Shorten says the coalition would only be able to make $1.7 billion in savings, not $3.7 billion as the coalition claims, from not proceeding with Labor's low income super plan.
"What we have done is we have based our calculations, saying the coalition's got more answers to explain than even we initially thought they did," he told Fairfax Radio.
"When you look at promises that the coalition's made to reintroduce a tax on low-paid workers, we have calculated that they would do that from 2015/16."
But Mr Shorten says the only way the coalition can reach that $3.7 billion figure is if superannuation contributions are taxed retrospectively, and he urged them to clear up the discrepancy.
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.
Mr Shorten was defending Prime Minister Kevin Rudd's claim of a $10 billion hole in opposition costings.
Shadow treasurer Joe Hockey says the claim is wrong.
"Three-quarters of the way through the campaign, we've released the great bulk of our costings," he told Fairfax Radio.
"They not only have been through the parliamentary budget office, but they are going to be verified by three independent people.
"Every policy we have put out there that involves money, we've put the cost of the policy against it."
