The payout, originally announced with the bank's second-quarter earnings last week, is the fourth distribution so far and takes the total amount returned to the investors to roughly $5.9 billion
"Over three and a half decades, I have personally worked at and led several banks in different countries and have lived through many crises," the former Lloyds chief executive said during Credit Suisse's webcast annual general meeting.
"What has happened with Credit Suisse over the last eight weeks, with the US-based hedge fund and the supply chain finance funds matters, certainly goes beyond that."
The Swiss bank said in a brief statement that Andreas Gottschling, the head of the board's risk committee, would not seek re-election at a general assembly.
Its shares fell 5.7%, with analysts pointing to the further Archegos hit and dilution caused by the issuance announced on Thursday of bonds convertible into 203 million shares.
In response, the bank is cutting its prime brokerage business, which caters to hedge fund clients, by about a third.
The probe is likely to be independent and carried out on behalf of the Cabinet Office, the BBC said. Reuters has not been able to independently verify the reports.
In his first comments on the row on Sunday, Cameron said that in his representations to government he was breaking no codes of conduct and no government rules.
Its demise has now created massive uncertainty for clients, who depended on its finance services to pay their bills and could now potentially default on payments and lead to further turmoil.