The three main global rating agencies - Moody's Investors Service, Standard & Poor's, Fitch ratings - all rate Australia AAA, although the latter two have a negative outlook, which means it could be cut in the next two years.

Asked on Sky News whether it would be a failure for the government if the rating was cut, Senator Birmingham said: "We are not expecting that to happen."

"The ratings agencies themselves issued their own statements, in their own words, last week in which they were very positive about the government's strategy in this budget and the approach we are taking," he said.

A credit rating downgrade would potentially raise the cost of borrowing for government and big business and banks in overseas markets, which in turn could be passed on to consumers.

But AMP Capital chief economist Shane Oliver thought it would mainly impact the "national psyche" rather than have a real economic impact.

Shadow treasurer Jim Chalmers believes the budget risks leaving too many people behind, even as the economy recovers.

He thinks that in a budget that included $100 billion in new spending, Australians doing it toughest were barely an afterthought.

"It's not a recovery if we go back to the type of inequality and immobility which has characterised the Liberals' eight long years in office," Dr Chalmers told an event run by peak welfare group ACOSS.

Opposition Leader Anthony Albanese laid out in last week's budget reply speech his $10 billion plan to build 30,000 social and affordable homes over five years through a Housing Australia Future Fund.

"After eight long years of this government, housing affordability has gotten worse and there are more homeless Australians than ever before," Dr Chalmers said.

But Prime Minister Scott Morrison told reporters in Brisbane the government had been successful in its partnerships with the states and community organisations in delivering affordable housing.

"We invest a great deal when it comes to affordable and social housing initiatives," he said.

He said Labor's plan would get less value for taxpayers' money.

In government, Labor would also pursue targeted support, or place-based initiatives, for disadvantaged communities.

"Recent studies, inquiries and reports, including important work by the Productivity Commission, have identified place-based solutions as an opportunity to change outcomes and get better bang for buck in social spending," Dr Chalmers says.

It would also seek private capital from socially minded investors, otherwise known as impact investing.

Dr Chalmers said in mature financial markets like the US and UK, impact investors had provided support for social sector organisations to finance housing, community education facilities, health centres and energy projects.

"We need to make sure that more Australians can get ahead in the recovery and aren't left behind," he says.

"That's why the budget was a missed opportunity, and an expensive one at that."

Australian Associated Press