Students and hire staff pay for Labor election pledges

Hiking international student visa fees and trimming consultant spending are Labor's plan to keep the budget in shape while splashing out on election sweeteners.

An assurance by Treasurer Jim Chalmers that more than $7 billion in savings would offset the cost of his party's election promises follows a stern warning from ratings agency S&P Global.

Australia risks losing its coveted AAA credit rating, the agency said, as spending soars from ill-disciplined state governments and federal election promises.

Labor's pre-election costings claim a crackdown on the use of consultants and labour hire in favour of public servants would save the public purse $6.4 billion.

An extra $760 million would come from bumping up international student visa fees to $2000 from $1600.

Finance Minister Katy Gallagher said the fee hike amounted to a "small uplift".

"We think that's a sensible measure that really prices the value of coming here and studying in Australia," she told reporters in Brisbane.

Dr Chalmers said the savings and extra revenue would leave public finances roughly $1 billion better off over four years compared to the pre-election economic and fiscal outlook.

"We will finish this election campaign with the budget in a stronger position than at the start of the election campaign," he told reporters on Monday.

He urged Opposition Leader Peter Dutton to show his hand on secret cuts to pay for nuclear reactors.

"The risk to our AAA credit rating is Peter Dutton and the coalition."

Hours before Labor revealed its costings, S&P alerted the major parties to the dangers of promising higher spending at the same time as eroding the Commonwealth's revenue base.

"The (federal) budget is already regressing to moderate deficits as public spending hits post-war highs, global trade tensions intensify, and growth slows," the ratings agency said in the report.

"How the elected government funds its campaign pledges and rising spending will be crucial for maintaining the rating."

Credit ratings assess a government's ability to service debt, with a score of AAA denoting the lowest risk.

Losing the top rating would make government borrowing costs more expensive.

Shadow treasurer Angus Taylor said coalition costings would be released in coming days.

A better budget position, lower taxes and a stronger economy could be expected under a Dutton government, he promised.

"If we continue in this way for another three years, S&P has said, that our credit rating is at risk, here's the price you pay for that," Mr Taylor told Sky News on Monday.

The coalition has pledged to cut 41,000 positions from the government workforce to lower costs, in contrast to Labor's strategy to trim "expensive" external contractor and consultant spend.