Unaoil executives "were also interviewed… in the presence of British officers in connection with a case of vast corruption with international ramifications that involves many foreign companies active in the petroleum sector," the Monaco government's statement said. Former Primary Health Care chief executive Peter Gregg. Credit:Daniel Munoz Fairfax Media revealed on Thursday that the British police had teamed up with the Australian Federal Police, the US Department of Justice and the FBI to investigate the vast cache of leaked Unaoil emails on which our stories have been based. Unaoil was hired over almost two decades by large multinational firms, including the offshore arm of Australia's Leighton Holdings, to pay bribes to top overseas officials in return for winning government funded contracts in oil-rich nations. Fairfax also revealed that the chief executive of Primary Health Care, Peter Gregg, was under criminal investigation over a $15 million payment he allegedly made in a former job as chief financial officer of Leighton Holdings.

He appears to have signed documents making the payment to a United Arab Emirates firm, Asian Global Projects and Trading, to guarantee the supply of steel to the Australian construction giant at "preferred and commercially beneficial" prices. No steel was ever supplied and Fairfax Media has obtained documents revealing the Dubai company that received the money has engaged in bribery and money laundering. Primary said it not only knew that Mr Gregg was under investigation at the time the company appointed him CEO in February 2015, but "remains comfortable with the performance and conduct of Mr Gregg since he was appointed". "As there is an ongoing investigation in progress, it is not appropriate for us to comment further on the matter raised in the media articles," the company said. Mr Gregg threatened legal action against Fairfax Media and reporter Nick McKenzie. Mr Gregg denied he had broken any laws and claimed the story was incorrect. Fairfax Media responded to Mr Gregg's lawyer, saying the story was accurate and Mr Gregg had declined repeated requests to respond to specific questions about the $15 million payment. Fairfax Media can now separately reveal that executives of Sydney private company Sinclair Knight Merz are under police investigation for alleged illegal payments made prior to 2012.

The company was sanctioned by the World Bank in 2013 over illicit payments made in Asia, but a source has now said the alleged activities may not have been fully known to the World Bank at the time. A source with intimate knowledge of the company's operations says at least one Australian manager appears to have encouraged bribery. SKM was acquired in late 2013 by US engineering giant Jacobs, whose spokesman confirmed this week that the company was under investigation and said he was "confident that all reportable matters have been disclosed to authorities and are being dealt with appropriately". Opposition Leader Bill Shorten said revelations of Australian companies' involvement in bribery and corruption were "tremendously alarming", while Justice Minister Michael Keenan said the government was committed to fighting corporate graft. It is understood Mr Keenan is pushing his coalition colleagues to support the beefing up of the nation's anti-corporate corruption regime. Mr Shorten said on Friday: "I'm grateful for the lid being ripped off some of those carryings on of multinational companies engaging in global bribery."

"When it comes to anti-corruption, Mr Turnbull's always out there bashing the unions, but he's been disappointingly silent on the conduct of Australian multinationals engaged in global bribery." Later this month, Labor and independent senator Nick Xenophon are planning to use a Senate inquiry to grill the allegedly corrupt Australian executives exposed in the Unaoil scandal. In the latest revelations to emerge from the trove of Unaoil's email traffic, Fairfax Media has discovered the deep involvement of a number of well-known Asian companies who worked with Unaoil. The emails reveal corruption inside Malaysia's national oil company Petronas, as well as South Korean titans Hyundai and Samsung, and even the Chinese government giant Sinopec. The oil industry's biggest ever scandal has also exposed Asian conglomerates Yokogawa of Japan, South Korea's ISU, Singapore's Keppel and Malaysian firm Ranhill. The emails show some Asian executives are enthusiastic participants in graft, underscoring the pervasive culture of corruption across the region. It's an alarming proposition as Asian companies develop into some of the most powerful and influential players in global business.

In one email, Korean ISU vice president Joon Lee, writing from a private address, urged Unaoil to bring cash to a meeting to pay a senior Libyan government official who could help ISU win a construction contract. "You are requested to come to see him as you told me at a hotel… I suggest to you with around 20,000 Eruo [euro] at this visit," the email to Unaoil said. The leaked files show a senior Samsung manager, in cahoots with executives from Hyundai, agreeing to pay bribes worth millions of dollars to rig oil-refinery contracts in Algeria. Unaoil also corrupted senior figures inside Malaysia's Petronas, paying kickbacks to secure their help to award contracts to Unaoil's clients on a major oil field in Iraq. In China, the files reveal that a senior manager from Sinopec subsidiary ZPEB demanded kickbacks from Unaoil in return for getting Sinopec to work with the corrupt Monaco firm.

The manager "is a player," states a Unaoil file, "and asked initially for 2% to cover all the ZPEB players, then over the 3 days [they] agreed to 1%". Unaoil's Chinese ventures began in 2003, when the company teamed up with an Asian businessman called [Mr] Wang. "[Wang] does have some access to Sinopec … and says that he has clear access to the Deputy Prime Minister, the Deputy President, and, if he wants, the 'Emperor' – ie. Jang Zei Ming … who is the real power still in China despite giving up the Presidency," wrote Unaoil employee Peter Willimont in an internal briefing. "As our deal stands with him now, it is 50/50 with him taking care of his end and us doing our bit."