Rating agencies have warned the Federal Government its triple-A credit rating is at risk as doubts grow about key spending cuts being delivered.
As Labor accused the Government of trying to double count infrastructure spending, Fitch Ratings said the economy and Budget showed vulnerabilities that could ultimately expose the country to a credit downgrade.
The mid-year Budget update revealed total debt would climb to a record $647 billion by the middle of next decade.
Forecast deficits have blown out more than $26 billion over the next four years, with no surplus expected before 2020-21.
Fitch says Australia risks a downgrade because of its debt and reliance on commodities. 
"Fiscal balances have started to fall behind many of the 11 other AAA rated sovereigns," it said.
"A failure to rebalance the economy away from mining is a potential risk over the medium term, which could put pressure on public finances and Australia's credit rating." 
The increase in expected Budget deficits is being driven by a $33.8 billion writedown in revenue for the Commonwealth.
Treasurer Scott Morrison has unveiled $10.6 billion  of savings, including removing bulk-billing incentives for pathology services, fewer incentives for MRIs and a cut in oncology incentive payments.
Health groups attacked the measures but Mr Morrison said the Government was focused on measured Budget savings.
"I've got a simple message to all those who take issue with the savings measures: show us your alternatives," Mr Morrison told ABC radio.
The Budget already has $13 billion of savings yet to pass the Senate.
Opposition Leader Bill Shorten said yesterday Labor would not back some of the more contentious measures, including the $650 million saving from changes to bulk-billing.
"Labor will oppose the idea that Malcolm Turnbull's Liberals have that the only way that Australia can get ahead is by attacking Medicare," he said.
The Budget update confirmed spending on duplicating Armadale Road for $116 million as promised by the Government during the Canning by-election.
But it also showed Armadale Road and projects in Queensland and SA worth a combined $1 billion would have to come out of the infrastructure budget.