He spoke at the bank’s annual meeting, a few hours after Credit Suisse withdrew from re-election the head of its board’s risk committee,

Andreas Gottschling.

Major Credit Suisse shareholders had targeted Mr. Gottschling over the recent failures and said they would vote against his reappointment.

Archegos, the family office of

Bill Hwang,

wreaked havoc across Wall Street when heavily leveraged bets it made on a small collection of stocks unraveled in March and triggered huge losses at some of its lenders. Credit Suisse had lent more to Archegos relative to its size than other banks and was one of the last to exit from its stock positions, The Wall Street Journal previously reported.

Last week, Credit Suisse raised fresh capital to shore up its balance sheet and Swiss regulators said they started enforcement proceedings over possible risk-management shortcomings.

Swiss regulators are also investigating the bank’s handling of Greensill. Credit Suisse is liquidating $10 billion in investment funds that the companies ran together.

Mr. Horta-Osório said what happened at Credit Suisse in the last eight weeks goes beyond a company’s regular ups and downs.

“A tough period and hard decisions lay ahead of us,” he warned.

Mr. Horta-Osório is one of Europe’s most highly regarded bankers after turning around Lloyds, which required a massive state bailout following the financial crisis. He narrowed its strategy around domestic U.K. banking, changed sales incentives and shed its part-government ownership.

The Portuguese-born banker now becomes the face of the Credit Suisse cleanup efforts. He signaled that chunks of the bank or riskier business areas could be carved out. Credit Suisse has said it would scale back the prime brokerage business that carried out trades for Archegos. It recently moved an asset management division that ran investment funds with Greensill into a separate unit, a move analysts say could be a precursor to a sale.

Mr. Horta-Osório also said the bank will review its culture, pay and incentives, with a focus on personal responsibility and accountability of staff.

“We need to foster a culture that reinforces the importance of risk management,” he said.

Credit Suisse Chief Executive

Thomas Gottstein,

who also spoke at the event, has the board’s confidence, Mr. Horta-Osório said.

In a rare apology from Credit Suisse, Mr. Gottstein said the bank deeply regretted the “significant and understandable concerns” shareholders, customers and employees have over Archegos and Greensill.

The departing chairman,

Urs Rohner,

also apologized for disappointing clients and shareholders, “and not for the first time.” He was at the bank 17 years, 10 as chairman, in a period that was punctuated by regulatory fines and scandal.

Credit Suisse sought to become safer by cutting sharply back in markets trading last decade and focusing on private banking and wealth management. But it continues to have a sizable investment bank to serve those wealthy clients and other customers. Even before the recent episodes, concerns repeatedly were raised by some shareholders about its risk management and culture.

In 2014, Credit Suisse paid $2.6 billion and pleaded guilty in a settlement with the U.S. Justice Department for conspiring to aid tax evasion by wealthy Americans. It paid $5.3 billion in 2017 over toxic mortgage securities sold before the 2008 financial crisis. The bank faces civil lawsuits and regulatory fines over $2 billion in fraudulent loans in Mozambique, and a former client is suing the bank for around $800 million for ignoring alerts that a Credit Suisse banker stole from him for years.

Some investors complained before Friday’s investor meeting, held at a mostly empty conference center near Lake Zurich, that they weren’t allowed to ask live questions for a second year because of coronavirus restrictions. Credit Suisse said it would come back with answers on some submitted by Ethos Foundation, representing Swiss pension funds that own between 3% and 5% of Credit Suisse shares.

Other board directors got lukewarm approvals.

Richard Meddings,

a veteran British banker who joined the board last year and heads its audit committee, got an 85% “for” vote, down from his 98% approval last year when he was elected. Mr. Meddings will take over Mr. Gottschling’s role on an interim basis as risk committee head, Credit Suisse said. Shareholders will have to vote on the appointment.

Blythe Masters,

a former

JPMorgan Chase

& Co. executive stepping onto the board this year, received just under 83% “for” votes to join.

Write to Margot Patrick at margot.patrick@wsj.com