In his annual report tabled in state parliament, Independent Commissioner Against Corruption Bruce Lander, says his office has conducted 250 corruption inquiries with 12 people convicted and a further 17 before the courts.

Mr Lander says the low number is unsurprising and in his opinion, an investigation that reveals no wrongdoing is as successful as one that goes to court.

"In the end, our investigations follow the facts rather than a preconceived outcome," he said in his report released on Tuesday.

"If the investigation reveals that there is insufficient evidence to warrant further action, so be it."

But the commissioner said it was often the case that matters couldn't be prosecuted because the improper conduct had effectively been condoned.

"Poor practices, policies, procedures and record keeping often means that matters of impropriety, often involving the misuse of public money, cannot be dealt with appropriately because of the state of the evidence," he said.

Mr Lander's comments followed criticism earlier this year of his office during parliamentary hearings into proposed legislation to allow him to investigate into maladministration in public.

Prominent QC Michael Abbott told a parliamentary committee the commissioner's corruption inquiries were "nothing less than trial by ambush".

Mr Abbott said Mr Lander had the power to conduct his investigations as he saw fit.

The commissioner hit back when he came before the committee, declaring Mr Abbott's claims were wrong in fact and misunderstood the law.

In his annual report, Mr Lander said he still believed maladministration remained the biggest threat to public institutions in SA.

"Maladministration infects numerous public institutions and results in significant and unnecessary loss of public money," he said.

"Corruption and maladministration are inextricably linked.

"Maladministration, by way of poor practices, policies, procedures or poor oversight and management, creates the opportunities for corruption to occur."

Australian Associated Press