Labor has dismissed coalition claims of a $67 billion black hole in its spending promises as a scare campaign.
But Malcolm Turnbull insists "Billion Dollar Bill" is outspending the government by 20-to-one ahead of the July 2 election.
The coalition is seeking to return the election agenda to its preferred ground of economic management, as a new poll shows Labor is gaining traction with its health and education promises.
Opposition Leader Bill Shorten, who campaigned in Perth on Tuesday, added to his raft of health policies by announcing a Labor government would within 100 days legislate to prevent Medicare ever being privatised.
"The repeated threats to Medicare posed by the Abbott-Turnbull government make such an unprecedented step necessary," Mr Shorten said.
The prime minister said the government could only fund promises such as Tuesday's pledge of an extra $60 million to fix mobile phone black spots because of "living within our means".
"Billion-dollar Bill keeping on joking about the spendometer," Mr Turnbull said on the campaign trail in the marginal Victorian seat of Corangamite.
"He has no way of paying for it other than by even higher taxes than the ones he's proposing."
Treasurer Scott Morrison and Finance Minister Mathias Cormann's explanation of Labor's $67 billion spending blowout descended into farce when they admitted during the Canberra media conference the figure could be $32 billion.
Labor frontbencher Penny Wong said the coalition figures included $19 billion of foreign aid spending, which was not the party's policy.
"They are happy to make things up," she said.
The government's budget priority of a $50 billion corporate tax cut risked pushing out the deficit and debt and making essential services less affordable, she said.
The latest Newspoll shows voters consider health as a more important issue than the economy and Labor better placed to manage health.
But Mr Turnbull is considered the better economic manager by 42 per cent of voters, compared with 38 per cent for Mr Shorten.
Mr Shorten announced $45 million to ease congestion along Perth's northwestern corridor in the marginal Liberal seat of Cowan.
Labor's campaign was sidetracked by Northern Territory senator Nova Peris' decision not to contest the election.
Senator Peris, the first female indigenous woman elected to parliament, is understood to be seeking a senior role with the AFL.
The party's national executive will meet in coming days to find a replacement, possibly journalist and former NT government minister Malarndirri McCarthy.
Mr Turnbull and Mr Shorten will face off in the first formal leaders debate of the campaign on Sunday night.
Mr Morrison later told the ABC the coalition would change its "black hole" claim figures if Labor fully backed its 90 per cent in foreign aid cuts.
"If they want to crab walk away from things they said earlier ... fine, we will adjust those numbers."
