Interstate companies and contractors may find it more difficult to secure South Australian government contracts under changes to the state's spending rules.

The government spends $8.5 billion a year on goods and services across areas such as hospitals, schools and various departments and agencies.

Under the procurement reforms, it will lift the spend allocated to SA businesses by five per cent or about $425 million.

In other changes, local workers must deliver at least 90 per cent of labour hours on major infrastructure projects and any contracts worth more than $55,000 awarded to interstate or overseas suppliers must be approved by a departmental chief executive.

At least 20 per cent of labour hours on major projects will be required to be delivered by apprentices, trainees, Indigenous workers and the long-term unemployed.

Treasurer Stephen Mullighan said the government should support local suppliers and local jobs wherever possible when spending taxpayers' money.

"These changes are designed to get more public spending into the pockets of local businesses and workers," he said.

"Awarding South Australian contracts to South Australian businesses, and keeping those dollars in our state, is a no-brainer."

An independent complaints process will be established for those who feel they have unreasonably missed out on government work and an annual project pipeline will be published detailing upcoming infrastructure projects over $10 million.

Public projects above $500 million will be broken into smaller stages or components to allow multiple South Australian companies the opportunity to participate unless the nature of the project makes it unfeasible.