"Simply saying the 'economy' or 'growth' will pay for new spending or tax cut plans is no plan for a sustainable budget repair strategy," shadow treasurer Chris Bowen said.

S & P Global Ratings in a research note released Friday reaffirmed its AAA rating on Australia's sovereign debt, but lifted its outlook to "stable" from "negative" thanks to an outperforming economy and swelling public coffers.

"Steady" government revenue growth will be supported by "the strong labor market and relatively robust commodity prices", complemented by "expenditure restraint", the analysts said.

"We expect the general government fiscal position to return to surplus by the early 2020s, as the central government's continued focus on fiscal prudence turns higher revenue collection into better budget performance."

S & P's "general" government fiscal position includes the federal and state budgets, and its analysts expect the federal budget to return to surplus by 2019-20.

"We expect large infrastructure spending at the state government level to likely keep the general government balance negative till fiscal 2021," the S & P analysts said.

The rating agency's announcement comes as the government committed an extra $4.6 billion in extra funding to Catholic and independent schools and following reports by The Australian Financial Review of a potential fast-tracking of small business tax cuts ahead of an election to be called by May next year.

S & P Global Ratings sovereign analyst Anthony Walker said "bipartisan support for a return to surplus" limited the risk to the surplus forecasts even in the event of a change in government.


"We believe both [parties] will get there, if by different channels," Mr Walker said.

The upgraded outlook was "fully justified", Bank of America-Merrill Lynch head of Australian economics Tony Morriss said, given improvements in government revenues and the improvement in economic conditions since the negative outlook was announced in July 2016.

"It is good news for Australian assets and the dollar, but perhaps not such big news as the above factors have been in play for a while and are well understood," Mr Morriss said.

The currency was largely unmoved, trading at $US72.9¢ in early afternoon trade.

Mr Morriss said the timing of the announcement was "interesting considering the clouds from trade wars and the downturn in the housing sector, not to mention the rise in political uncertainty ahead of the next federal election".

Mr Walker said the ratings agency was, for now, "comfortable" around the potential risks from trade tensions, but noted that a "sharp escalation of the trade war could have negative consequences on Australia".

Critically, the S & P's analysts remained sanguine on the potential economic impact of a weakening housing market.

In its Friday update, the ratings agency's analysts said they "expect property prices to continue their orderly unwind, and that this slowdown won't weigh heavily on consumer spending and the financial system's asset quality".


Mr Walker said that double-digit credit growth driving runaway house price increases was part of the reason the ratings agency downgraded its outlook in 2016.

The rating "could come under pressure if house prices fall sharply and increase risks to fiscal accounts, real economic growth, and financial stability".

S & P also said it could lower the rating should it "consider it unlikely" that the budget will return to surplus within the next five years.

S & P has had a negative rating outlook on Australia since July 2016, and a AAA rating since February 2003. Australia is one of only 11 countries to earn the highest rating from S & P, alongside the likes of Canada, Germany, the Netherlands, and Switzerland.