South Africa has lost R700-billion to corruption over the last 20 years, the Institute of Internal Auditors said on Wednesday.

"The cost of corruption in the last 20 years... we have lost R700-billion," CEO Claudelle von Eck said at the launch of the Anti-Intimidation and Ethical Practices Forum in Johannesburg.

Von Eck, who is the forum's chairperson, said people who tried to report corruption were often muzzled.

"Members are being intimidated when they try and raise the issue of corruption in an organisation."

Von Eck said the forum aimed to educate its members about corruption, advise them how to reveal corruption, and what to do when whistle-blowers were intimidated.

It was intended to be a professional collective voice which would make pronouncements about the state of governance in the country.

"We cannot be silent. As professionals we should be able to say this is what the state is, this is what we need to do to rectify things."

The forum consists of an executive committee, agencies who can take action, interested organisations, and an evaluation panel.

"As professionals we have a responsibility, an understanding that our responsibility does not begin and end just at our desk and just at our jobs. We've got to carry South Africa," she said.