Election promises made by government and opposition parties will be subject to compulsory post-election auditing under plans to be announced by Treasurer Wayne Swan.
The move means unfunded spending proposals, double-counting of savings, and other common pre-election vagaries will be subsequently exposed, acting as a strong disincentive for any political party likely to win the election.
The Treasurer's fiscal snooker reflects his growing charge that the Coalition has failed to address a significant hole in its costings that the government says allows it to make promises without having to say where the money is coming from.
It will be outlined in a speech to Australian Business Economists in Sydney on Friday that is also designed to set out the global and national economic outlook facing the government as it frames a politically crucial pre-election budget.
The mandatory audits will be undertaken by the recently created Parliamentary Budget Office and will apply to any spending and savings measures offered in the election period.
"Transparency would be further enhanced if the PBO were to prepare a post-election audit of all political parties, publishing full costings of their election commitments and their budget bottom line 30 days after an election," he will say.
"We will introduce legislation for consideration by the Parliament to enable this reform.
"This will remove the capacity of any political party to try to mislead the Australian people and punish those that do."
Among other aspects of the speech, Mr Swan will commit to keep Australia's ratio of tax to gross domestic product at or below its current level of 23.7 per cent "on average".
"We'll continue to ensure that real spending growth averages no more than 2 per cent growth over the forward estimates – compared to around 3.7 per cent on average over the 10 years before the GFC [global financial crisis] under the previous government. We'll also keep taxation as a share of GDP, on average, below the 2007-08 level of 23.7 per cent."
During the 2010 campaign, Labor and the Coalition delayed the release of their costings until days before the vote, denying Treasury the opportunity to check their calculations. Treasury later found errors in the Coalition costings it said amounted to $3.5 billion.