Finance Minister Katy Gallagher says Labor has spent its first months delivering on a promise to undertake a deep audit of spending to identify where money can be returned or redirected.

Tuesday's budget will include more than $21 billion in savings and decisions to redirect existing spending, she said.

Examples include the retrieval of $6.5b from infrastructure projects to better align the investment with construction market conditions.

A further $3.6b will come from slashing expenditure on external labour, advertising, travel and legal costs.

More than $2b will be shaved from various grants programs.

Senator Gallagher said funding some big infrastructure projects would be delayed beyond forward estimates, with some experiencing issues accessing materials and workforce.

"It's very sensible to look at where we can find some reprofiling but there will also be some genuine savings," she told the ABC.

"It's not exclusively infrastructure, we are finding savings across government, we have gone to every single department and asked them to look at their programs to identify those that don't need to be done any longer or don't align with government priorities."

Senator Gallagher flagged "significant investment" to repair flood damage, and backed Emergency Management Minister Murray Watt's flagging of Australia building a semi-professional disaster relief workforce.

"The reality is we're seeing more and more (natural disasters), more is being asked of volunteers responding to these emergencies and we have to be looking forward and looking at how we can deal with this in the best way," she said.

Senator Gallagher said there would likely be more emergencies due to the impacts of climate change and Australia needed to ensure emergency responses were resourced properly.

Shadow treasurer Angus Taylor said Labor had been gifted the lowest unemployment rate in decades, economic growth of more than three per cent and an improving budget bottom line by the coalition.

He said a high-taxing, high-spending Labor budget would only make the Reserve Bank's job harder and that Treasurer Jim Chalmer's challenge would be a test of his willingness to put Australians first.

"Budgets are statements of a government's priorities and ... this new Labor government's true intentions will be exposed," he said.

"In a rapidly changing economic environment, Labor must use the budget to deliver a coherent plan to deal with the current cost of living crisis which is very real and painful for so many Australian families."

Mr Taylor urged Dr Chalmers to put downward pressure on inflation and interest rates without increasing taxes and deliver relief to supply side pressures in the economy by increasing productivity and participation.

Opposition finance spokeswoman Jane Hume said the budget needed to address inflation and not "deteriorate" the bottom line.

"What we want to see is that the budget tomorrow builds on the strong position the government inherited from the coalition," Senator Hume told ABC Radio.

Senator Hume said the $2.2b set aside for Victoria's massive Suburban Rail Loop transport project as a "political" decision, with the Andrews Labor government facing a state election next month.

Australian Associated Press