Elmer Funke Kupper has resigned with immediate effect as managing director and chief executive of the Australian Securities Exchange (ASX), to focus on an Australian Federal Police (AFP) investigation into his previous employer.
The ASX board said that Chairman Rick Holliday-Smith would become executive chairman while the stock exchange operator searched for a new head.
The shock resignation comes less than a week after newspaper The Sydney Morning Herald reported that gaming company Tabcorp had allegedly paid $200,000 to the sister of Cambodian Prime Minister Hun Sen in early 2010, when Funke Kupper was Tabcorp's CEO.
The SMH reported on March 15 that the payment was made during a period in which Tabcorp was attempting to secure an online gaming license in Cambodia, and that the payment was being investigated by Australian and foreign anti-bribery agencies.
Following the SMH report, Tabcorp released a statement saying that it had explored an opportunity in 2009 related to the possible deregulation of Cambodia's sports betting sector.
"Tabcorp chose not to pursue the opportunity and the business was never operational," the statement said.
"Today we were advised by the Australian Federal Police that they have commenced an investigation in relation to this matter. Tabcorp will fully cooperate with the investigation."
In a statement released just prior to the local market close on Monday, ASX said, "The ASX board accepted that Elmer wanted to direct his full focus to the investigations which may be made into the Tabcorp matter - and not have them interfere with the important role of leading the ASX.
Funke Kupper, who remained a director of Tabcorp after leaving the company for ASX in 2011, also took leave of absence from Tabcorp's board on Monday.
Five days ago the ASX boss told the SMH that he had no intention of stepping down from the Tabcorp board, while Holliday-Smith told the paper that he was "not aware of any reason" Funke Kupper should step down from his role that ASX.