An inquiry into a controversial South Australian parliamentary allowance is being hampered by claims that material requested by the state's corruption watchdog may be protected by parliamentary privilege.
Independent Commissioner Against Corruption Bruce Lander last month began an inquiry into the country members accommodation allowance which is paid to country MPs when they need to stay in Adelaide for parliamentary and other business.
Errors made in some claims by MPs recently resulted in two ministers, Stephan Knoll and Tim Whetstone, quitting state cabinet and repaying some money.
On Friday, Mr Lander said he had asked MPs and their staff for information relating to allowance claims but some had declined to provide the material.
"Those members and their staff have asked me to delay my request for documents and information until parliament has determined whether or not a claim for parliamentary privilege is to be made," he said in a statement.
"I do not think that the documents or information sought would be protected by parliamentary privilege. However, the privilege is that of parliament."
With parliament in recess over winter, the issue cannot be resolved until it returns on September 8, which is after Mr Lander's current term as ICAC expires at the end of this month.
"Although I am continuing to seek evidence and information from other persons and sources, the potential for a claim for parliamentary privilege has had the effect of delaying the investigation," he said.
"I have not been able to examine documents and other evidence in the custody of the members and their staff, relevant to the matters under investigation.
"Also I have not been able to interview or examine the members or their staff."
Opposition Leader Peter Malinauskas said he had instructed all his MPs who claimed the allowance to comply with the request for information.
Premier Steven Marshall said he expected all MPs to comply with the laws in relation to the ICAC act.
"There are laws in relation to this and they must be followed," the premier said.
Mr Lander said whether or not his current investigation continues after he leaves his office would be a matter for his successor, former Supreme Court Justice, Ann Vanstone.