Treasury secretary John Fraser says it has been getting harder to forecast budget deficits and surpluses, and aggregates like GDP growth, as the global economy becomes more integrated.
He has also challenged the claim by Treasurer Scott Morrison that Australia does not have a revenue problem, saying successive falls in tax receipts have been the "main driver" of every budget downgrade since 2014.
Speaking publicly for the first time in 2016, Mr Fraser has set out the budgetary problems facing the Turnbull government this election year. 
It will prove to be another challenging year for Australia's economic authorities, he says.
Australia is facing yet another year of below-trend growth, lower than expected tax receipts, and lower income from falling commodity prices, he said.
Australia's fiscal position is now "a little more exposed" to shocks in global capital markets, he said, because around two-thirds of Commonwealth public debt is held by non-resident investors - a share that has risen since 2009 and remains historically high.
"Unexpected movements in domestic and global factors that drive Australia's economic growth and the economic outlook, including greater than anticipated movements in commodity prices and a number of broader political factors, have meant that in every Budget update since 2014, the fiscal outlook has been downgraded," Mr Fraser said.
"We are not in a crisis. But the budget is rightly a focus of attention."
Speaking at the Sydney Institute on Thursday evening, Mr Fraser said falling global commodity prices, combined with more moderate wage and price growth domestically, have seen Australia's nominal GDP growing at 50-year lows.
And while real GDP growth rates have remained "respectable" in the face of difficult global circumstances, it's nominal GDP that matters for revenue, he said.
The historically low nominal growth outcomes and lower growth projections, alongside historically high payments-to-GDP, mean it is taking longer for the budget position to return to pre-crisis levels compared with the cyclical downturns of the early 1980s and 1990s, he said.
"Much of the deterioration in the budget position has been the result of revenue collections falling short of forecasts as we experience the flipside of the mining investment boom," he said.
"Income tax receipts are being weighed down by lower than expected working-age population growth and weaker wages growth, as well as declines in commodity prices and weaker equity markets."
The impacts of successive revenue downgrades have only been partially offset by the government's structural saving measures, he said.
In real terms, government spending has grown at an annual average rate of around 3.5 per cent since 2007 compared with around 3 per cent during the 1980s and 1990s.
As a result, at 25.9 per cent of GDP, spending in 2015-16 is forecast to be close to the post-GFC peak, and could have been higher were it not for the measures taken by the government in the mid-year budget update.
Mr Fraser said the recent savings made by the Turnbull government are helping a little - Australia's payments-to-GDP ratio is now projected to decline over the next four years to 25.3 per cent by 2018-19, he said.
"But government spending will not get below 25 per cent at any time over the next decade," he warned.
It comes after Treasurer Morrison used his mid-year budget update to reveal Treasury's downward revisions to their assumptions underpinning Australia's medium-term growth projections.
It means Australia's potential growth rate has been officially lowered from 3 per cent to 2.75 per cent.
"These changes are crucial for the real GDP outlook for the final two years of the [four year budget period] - that is, 2017-18 and 2018 19 - which has been revised down from 3.5 to 3 per cent," Mr Fraser said.
"The nominal GDP and therefore the revenue projections for these years are now lower and more realistic," he said.
Mr Fraser said it was important that Australia maintain its top credit ratings because they help to contain the costs associated with servicing public debt.
He said Australia was one of only 10 countries with a triple A credit rating from all three of the major rating agencies, reflecting our reputation for fiscal prudence.
"But this rating is dependent on credible fiscal consolidation and a smooth transition to a more diverse economy.
"We should not be complacent about this. I know from personal experience during the financial crisis how important a strong credit rating is to investor confidence.
"If we are to permanently reduce net debt, we are going to need to achieve sustained 'structural' budget improvements.
Speaking on Friday morning, Prime Minister Malcolm Turnbull said that Australia's triple A credit rating was not under threat.
Mr Turnbull said ratings agencies had given a "very positive review of the government's strategy to move back into fiscal balance" as recently as the   December mid-year budget update.
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