Current Independent Commissioner Against Corruption Ann Vanstone said it was astonishing the state government was considering supporting legislation, just hours before it was passed in the upper house.

Ms Vanstone was particularly critical of changes she said would shield politicians from investigation at a time when two state MPs were before the courts on charges related to ICAC inquiries.

"The first thing about this bill, which hits one in the eye, is that the shelter for politicians, that is parliamentary privilege, is to be built into a 20-foot wall," she said.

"An immediate aim seems to be to protect themselves from scrutiny."

Ms Vanstone was also critical of proposed restrictions on her ability to speak publicly about investigations and said some of the changes would add considerably to the costs associated with keeping checks on corruption and maladministration.

"Let me be clear as to my position. If this or a similar bill is passed by the parliament, it will be plain that politicians do not want an ICAC in South Australia," she told the committee on Wednesday.

"It's as simple as that. This bill dismantles ICAC and the whole scheme designed to govern public integrity.

"It is based on misinformation about past events, a misunderstanding of the criminal justice system and it entirely ignores the exemplary way in which ICAC has been operating in the last year."

Despite securing the backing of all upper house MPs, the legislation must also be approved by the House of Assembly before becoming law.

SA-BEST's Frank Pangallo said his bill streamlined the powers and responsibilities of the ICAC to focus only on matters of serious and systemic corruption.

The legislation proposes misconduct and maladministration be investigated by the state ombudsman and a separate Office of Public Integrity be set up, along with the Office of the Inspector, that would have powers of oversight and report directly to parliament.

"Anti-corruption and integrity agencies have a critical role to play in our society because serious corruption and misconduct in our public sector must not be allowed to flourish unchecked," Mr Pangallo said.

"However, after eight years of substantial expenditure, secret investigations, underwhelming results, controversy and criticism, changes to the way ICAC functions are appropriate."

Mr Pangallo said his bill also provided mechanisms to protect people from reputational damage.

He said people under investigation, including those who were completely exonerated, had careers ruined and relationships destroyed.

Tens of millions of dollars had been wasted on investigations and criminal trials that should never have proceeded, he added.

"Anti-corruption and integrity agencies have enormous powers bestowed upon them, and it is a societal expectation they use these powers responsibly and within the law," Mr Pangallo said.

Australian Associated Press