The Coalition's efficiency dividend could rip $4.9 billion out of the public service if left in place for the next decade, a review by the Parliamentary Budget Office has found.
For the first time, the budget office has modelled the medium- to long-term impact of federal election promises from the three major parties, as part of its 2019 post-election report.
Labor made four times as many promises as the Coalition during the campaign, with a net impact of $17 billion, compared with $100 million.
The Coalition's commitment to extend public service efficiency dividend in the dying days of the election campaign had the biggest budgetary impact, helping to offset the cost of its 67 other commitments, the review said.
The measure would cut $1.5 billion from the public service over the next four years.
But the budget office estimated the dividend would remove $4.87 billion from departments if it continued as planned until 2029-30.
The Coalition said the dividend would save $5 billion over the medium term.
Of Labor's 273 promises, the changes to franking credits would have had the largest impact, saving $14.3 billion over the forward estimates.
The analysis also showed Labor's loan scheme for first home buyers would have been slightly cheaper than the Coalition's, as funding for research on housing demand, supply and affordability would have been funded separately.
It found bringing back the 30 per cent rebate for Australians with private health insurance would cost the federal government more than $3 billion each year by 2030.
The rebate was ditched in 2012 under the Gillard government, which brought in a means-tested scheme instead to stem a blowout in payments.
Health Minister Greg Hunt told the Press Club the government would take steps to restore the rebate once it had a healthy budget surplus.
"The definition of a sustainable surplus is one per cent, and at that point we will be able to take further steps to return to the 30 per cent," he told the event in May.
When asked about the comments, Prime Minister Scott Morrison told the office the minister's "qualified statement" didn't represent an election commitment with a "quantifiable impact on the underlying cash balance".
Mr Hunt had been talking about a review of existing reforms aimed at reducing private health insurance costs, the prime minister said.
"The further steps minister Hunt referred to reflect that the government will undertake a review of the implementation of the current reforms to ensure the reforms are meeting their stated intent."
The office determined the comment was not a "commitment" that should be included in its report, but noted the measure wouldn't come for free if implemented.
"The impact of restoring the private health insurance rebate to previous levels could have a budget impact of over $3 billion per year by the end of the medium term," the report states.
Mr Hunt's comments mark one of several policies the report refers to as "aspirational in nature" because parties didn't lock in details of how they would be considered.
Labor's target for 50 per cent of new cars bought in Australia in 2030 to be electric also fell into this category, as did the Greens' plan to legislate a minimum wage that was "at least 60 per cent of the adult median wage".
- with AAP