Australia's corporate watchdog has seized files belonging to the corrupt Monaco-based oil industry firm Unaoil as part of its criminal investigation into leading Australian executives, including Peter Gregg.
ASIC served Fairfax Media with a compulsory order to hand over the Unaoil files, which detail millions of dollars of offshore payments by Australian companies, including Leighton Holdings.
The ASIC order reveals the watchdog is investigating former Leighton executive Mr Gregg, who is now chief executive of a $2 billion Australian listed health firm, over alleged false accounting offences linked to a $15 million payment to a Dubai consultant in 2011. 
The Unaoil files, which were leaked to Fairfax Media last year, reveal the Dubai consultant is corrupt. They also separately implicate former Leighton senior executives David Savage, Russell Waugh and Peter Cox in major bribery and money laundering in the UAE and Iraq.
The dramatic development comes as a Senate committee is set this morning 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.
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.
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 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 ASIC order reveals the corporate watchdog is also seeking evidence about the Dubai consultant who received the $15 million payment.
The 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 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.
The ASIC orders state 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.
Fairfax Media provided the records after ensuring they did not disclose confidential sources' identity.
The $15 million 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.
Mr Gregg is the chief executive of ASX listed company Primary Health Care, whose board and chairman Rob Ferguson are backing him.