Former Leighton executive Peter Gregg. Credit:Daniel Munoz The dramatic development comes as a Senate committee is set on Fridaymorning to call a confidential police and ASIC witness in what may be an explosive hearing into alleged corporate crime. The witness is former senior Leighton executive Stephen Sasse, who is understood to have unsuccessfully tried to confront corruption in the company before being contacted by federal agents in 2012. The senate hearing will probe suspect offshore payments, and why ASIC and the federal police are yet to charge a single individual linked to the long-running Leighton scandal.

In an unrelated hearing last year, Mr Sasse gave evidence at the union royal commission into his dealings with Opposition Leader Bill Shorten while Mr Sasse was a construction executive and Mr Shorten was a union boss. This is likely to be seized upon by Labor to argue that the government is failing to pursue corporate corruption with the same zeal with which it has attacked alleged union crime. The hearing will intensify the debate about the Turnbull government's stance on corporate crime, and its move this week to boost the resources of ASIC. Alleged corruption involving Australian companies overseas is making global headlines due to the Unaoil scandal and the recent resignation of Australian Securities Exchange chief Elmer Funke Kupper. Mr Kupper resigned after Fairfax Media revealed he had allegedly overseen a payment to a relative of Cambodian Prime Minister Hun Sen while Mr Funke Kupper was the head of gaming giant Tabcorp. The payment, aimed at securing a Cambodian gaming licence, may have breached foreign bribery laws and is being probed by the federal police. On Wednesday, ASIC demanded Fairfax Media hand over the files from Unaoil, which worked for Leighton Holdings and dozens of major multinational companies. Unaoil paid bribes to win contracts and favours for multinationals in oil-producing nations.

The FBI, US Department of Justice and UK police have launched their own investigations into Unaoil. The ASIC document seizure orders reveal that Mr Gregg is under investigation for allegedly falsifying the accounting records of Leighton in connection to a $15 million offshore payment he directed the company to make in August 2011. The offence carries a maximum jail term of two years. The ASIC order reveals the corporate watchdog is also seeking evidence about the Dubai consultant who received the $15 million payment. The Unaoil files seized by ASIC show Mahesh Khemka, the Dubai-based consultant who was paid the $15 million, is a criminal involved in bribery, fraud and money laundering. Mr Gregg's fellow Leighton executives, David Savage and Russell Waugh, knew this before Mr Gregg made the $15 million payment in August 2011.

Just a few months earlier, in April 2011, Mr Waugh and Mr Savage had used Mr Khemka and Unaoil to pay a $5.6 million bribe to help win a contract for Leighton Offshore in Iraq. It was one of several large bribes Mr Waugh instructed Leighton's offshore business to pay via Unaoil. There is no suggestion Mr Gregg had any dealings or knowledge of Mahesh Khemka until August 2011. Leighton pipeline The ASIC orders state that the watchdog is investigating false bookkeeping offences in relation to "payments by the Company [Leighton] to" Mr Khemka in August 2011, as well as "suspected contraventions of … the corporations act … pertaining to payments made by the company and/or its subsidiaries to third parties during 2009 – 2011 to obtain construction contracts in Iraq". The ASIC orders caution that ASIC has not found that any law has been broken by an individual, but that an investigation is ongoing. ASIC has seized all records "sent, copied to, forwarded or received by Russell Waugh, Peter Gregg, David Savage, Peter Cox, Ata Ahasani [Unaoil chairman], or Mahesh Khemka".

Fairfax Media provided the records after ensuring they did not disclose the identity of any confidential sources. The $15 million Mr Gregg payment was ostensibly part of a deal to allow Leighton Holdings to purchase steel at a preferred price as part of a centralised procurement process. But no steel was ever supplied after the $15 million was paid. The documents seized by ASIC also suggest Leighton had no centralised steel procurement policy in place at the time of the $15 million payment. Mr Gregg has denied any wrongdoing, but has refused to answer specific questions and has instead sued Fairfax Media. Former senior Leighton executive Stephen Sasse. Credit:Ben Rushton

Mr Gregg is a former senior executive at Qantas, and is now the chief executive of ASX listed company Primary Health Care, whose board and chairman Rob Ferguson are backing Mr Gregg, even though he is the subject of an active criminal probe in connection to the payment. It is understood Mr Gregg paid the $15 million on the urging of fellow executive Russell Waugh and Indian businessmen as part of efforts by Leighton to revive a stalled Indian business deal. Loading Mr Savage has refused to answer questions but denied any wrongdoing, while Russell Waugh and Peter Cox have not responded to questions. Click here to contact our investigative reporters anonymously