It is understood that only a handful of those companies have reported to police their suspicions that their own staff have engaged in foreign bribery or other criminal conduct.

The revelations are likely to strengthen calls from the federal police to reform Australia's anti-bribery regime to encourage companies to disclose suspected corruption.

Deloitte senior partner Frank O'Toole said the upcoming Senate committee on foreign bribery by Australian companies should call for major changes to the nation's anti-bribery laws.

His comments come with the release by Deloitte of a survey of more than 250 senior executives from top Australian and New Zealand companies and public sector organisations.

The survey, released exclusively to Fairfax Media, found that one-third of all companies operating in high-risk offshore destinations, including Asia, Africa and the Middle East, had uncovered a suspected bribery or corruption incident over the last five years.

Almost a quarter of all executives surveyed said their firm had, during that same period, confronted corruption involving a staff member or contractor inside Australia.

The Australian Federal Police recently told a Senate inquiry it had more than a dozen active foreign bribery investigations.

Mr O'Toole said another alarming finding from the Deloitte survey related to the failure of many firms to have an adequate anti-corruption regime to detect and prevent graft in their overseas operations.

Forty per cent of executives interviewed from firms with an offshore operation "don't have (or don't know if they have) a formal compliance program in place to manage corruption risk".

"We haven't seen any tangible decrease in levels of corruption in recent years, or any major shifts in attitudes towards it, especially in offshore jurisdictions," Mr O'Toole said.

He said the findings highlighted the ongoing problems with the way Australia tackled white collar crime.

"We have heard a lot from the federal police about how they have ramped up their investigations of foreign bribery and that is no doubt true. But they are coming off a low base and there is still only two still unresolved prosecutions in the 15 years since foreign bribery laws were passed in Australia."

The AFP is preparing to charge several executives and companies in the coming months with foreign bribery offences.

Senior federal police have previously called for companies to be given incentives to co-operate with authorities, including a commitment to have self-disclosure recognised during sentencing.

In the United States, which has one of the more successful anti-foreign bribery regimes in the world, disclosure by companies or whistleblowers is encouraged through a series of incentives.

These include financial rewards for tip-offs and negotiated settlements with companies that co-operate with investigators.

The Senate committee inquiry into foreign bribery will start later this year.

It was established after Labor senator Sam Dastyari told Parliament he had evidence that major Australian firms had engaged in corrupt practices overseas.

Mr Dastyari was also critical of the failure of the Australian Securities and Investments Commission and the AFP to effectively combat the problem.

Former federal court judge Roger Gyles, who was recently appointed by the Abbott government to review the nation's terrorism laws and who also chairs the local branch of corruption watchdog Transparency International, recently told Fairfax Media that Australia's foreign bribery laws needed to be overhauled.

Mr Gyles said the key change was moving the burden of proof from prosecutors to those who have been shown to have made payments to foreign officials.

If the company cannot show a payment is legitimate, then a case may be proven, he said.