SYDNEY (Reuters) - Uncertainty around Commonwealth Bank of Australia's CBA.AX senior leadership deepened on Monday as the chief financial officer resigned unexpectedly, the fifth executive to depart in one of the worst governance crises in the bank's history.

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Australia’s biggest bank is struggling to rebuild its reputation after a series of scandals revealed flaws in its leadership culture, exposing it to closer regulatory scrutiny, higher compliance costs and potential fines.

Chief Executive Matt Comyn, who replaced Ian Narev in April with a promise to fix the bank’s problems, said he would need weeks to make headway in building his new team, raising concerns over upheaval in the leadership group.

“We are making good progress with the renewal of the bank’s executive team and I expect to provide an update on appointments to my leadership team in the coming weeks,” Comyn said in a statement to the bourse.

Australia’s banks are in damage-control mode as an ongoing independent inquiry into the financial sector exposes widespread misconduct, prompting calls for tighter regulation and stiffer penalties.

CBA is also facing potentially massive fines and higher capital requirements over breaches of anti-money laundering and terror financing laws, the result of “complacency” at the highest levels of management, according to a report released earlier this month by the banking watchdog.

In addition, CBA said last week it would settle with the Australian corporate regulator over allegations it manipulated the bank bill swap rate.

NEW CFO

Chief Financial Officer Rob Jesudason would depart “with immediate effect” to take an external role in Hong Kong, the bank said, just a over a year since he took up the role.

Alan Docherty, the previous CFO of the Institutional Banking and Markets unit, was appointed as acting CFO.

The change comes less than two months since the bank announced the departure of the three executives in charge of human resources, IT and institutional banking.

Brian Johnson, a banking analyst at CLSA, said the departure of Jesudason surprised the market so soon after the executive shake-up in March.

“While I’m positive on CBA, here’s the problem: we now have got a CFO, head of retail and banking services, head of institutional banking, head of human resources, head of enterprise services and head of marketing and strategy - that is, 6 out of 12 executive positions where they are conducting a search at the moment,” he said.

In December, CBA appointed Vittoria Shortt head of ASB Bank, its New Zealand unit, leaving her former position as Group Executive, Marketing and Strategy vacant.

CBA shares were 0.2 percent higher in afternoon trading, in line with the broader market.