Credit Suisse CEO Tidjane Thiam is resigning after almost five years on the job, acknowledging that a spying scandal caused "anxiety and hurt" and tarnished the reputation of the top-drawer Swiss bank.

The bank said in a statement Friday that its board had accepted Thiam's resignation a day earlier. It will take effect on Feb. 14, after the presentation of Credit Suisse's fourth-quarter results. He will be replaced by Thomas Gottstein, the CEO of the bank's Swiss operations.

The spying scandal erupted last year after the former wealth management chief, Iqbal Khan, said he was being spied upon by Credit Suisse after he joined rival bank UBS. An external investigation then showed that the spying operation had been ordered by Pierre-Olivier Bouee, then Credit Suisse's chief operating officer, to snoop on Khan and another former executives.

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"I had no knowledge of the observation of two former colleagues," Thiam said in Friday's statement. "It undoubtedly disturbed Credit Suisse and caused anxiety and hurt. I regret that this happened and it should never have taken place."

Bouee and the head of the bank's global security services quit over the scandal, Credit Suisse said in October.

The external investigation found no indication or evidence that Thiam knew anything or was informed about the surveillance operations.

Break down

The Financial Times and others report that Thiam's relationship with Chairman Urs Rohner broke down in the wake of the scandal. Major shareholders have backed Thiam as a talented and successful leader and urged the chairman to publicly support him.

Thiam, who is from Ivory Coast, is the bank's first African-born CEO and is a graduate of France's elite Ecole Polytechnique university. Last month, he was one of about two dozen CEOs and other business leaders who dined with U.S. President Donald Trump at the World Economic Forum's annual gathering in Davos, Switzerland.

FILE PHOTO: CEO Tidjane Thiam (L) of Swiss bank Credit Suisse listens as Chairman Urs Rohner speaks during the bank's annual shareholder meeting in Zurich, Switzerland, on April 28, 2017. Arnd Wiegmann / REUTERS

Rohner credited Thiam with making an "enormous contribution" and for returning the bank to profit.

"Under Tidjane's leadership, Credit Suisse simultaneously re-purposed our strategy, restored our capital, reduced our costs, de-risked our business, promoted diversity and engendered an exceptional level of co-operation between various divisions," he added. "Credit Suisse is in good health and we have a deep bench of talent which can build on his achievements."

The 164-year-old bank, which is perhaps best known for its wealth management and investment banking operations, has more than 45,000 employees and had nearly 1.35 trillion Swiss francs (dollars) of assets under management as of the end of 2018.