When Tidjane Thiam joined Credit Suisse as chief executive in 2015, he was charged with turning around the Swiss bank and steadying its profit.

A drive for revenue at any cost had pushed traders at Credit Suisse to take outsize positions in risky and hard-to-sell securities. As trading conditions soured, the bank had to cut thousands of jobs.

By 2016, Mr. Thiam had pivoted away from the volatile trading of its investment bank to enhance its more reliable wealth management division. Now that division has produced an unlikely, and embarrassing, corporate spy scandal.

The Swiss bank’s chief operating officer, Pierre-Olivier Bouée, resigned on Tuesday after a company board ordered an examination into his ordering the surveillance of its top wealth manager, who quit to work for UBS.

Mr. Bouée could not be reached for comment.

In August, Mr. Bouée ordered the Swiss bank’s head of security services to track Iqbal Khan, its head of wealth management, who was leaving after a personal disagreement with Mr. Thiam. Outside investigators were hired to follow Mr. Khan and see if he was trying to poach employees or clients in breach of his Credit Suisse contract.

But the investigation turned messy after a confrontation between Mr. Khan and a corporate spook outside a Zurich restaurant in mid-September.

Mr. Khan, who had left Credit Suisse weeks earlier, submitted a criminal complaint about the encounter, and Zurich’s public prosecutor now is investigating. The Swiss Justice Department also is looking into the death of a security expert involved in the surveillance, the prosecutor’s office said in a statement Tuesday. The office said it was examining the circumstances.

Urs Rohner, the chairman of Credit Suisse, said at a news conference on Tuesday morning that the surveillance of Mr. Khan was “wrong.”

“The measure that was taken was disproportionate and did not reflect the criteria and standards by which we measure our own work,” Mr. Rohner said. “The observation was wrong and inappropriate, even though the instructions were subjectively provided for the protection of our firm’s interest.”

The results of a Credit Suisse investigation into the episode, conducted by an external law firm for the board of directors, were announced on Tuesday. The board was told that the surveillance had found no evidence that Mr. Khan tried to poach employees or clients from Credit Suisse.

The investigation also found that Mr. Thiam and other executives had not been aware of the spying. Because of this, Mr. Rohner said, “we strongly reject any and all assertions made over the last days that call into question the personal and professional integrity of our C.E.O.”

The bank said on Tuesday that James B. Walker, who was chief financial officer for the United States, had been appointed to take over Mr. Bouée’s role. It also said it had accepted the resignation of the head of global security.

After several years of putting its house in order, the bank faced questions on Tuesday about whether Mr. Thiam had been properly informed about the surveillance — or what was happening under his management if he did not know that Mr. Khan was being watched.

“I don’t believe in my own mind, speaking as a board member, that that suggests that Mr. Thiam is not on top of the rest of the organization,” said John Tiner, chairman of the audit committee, during the news conference.

Mr. Rohner said there had been personal differences and “heated discussions” between Mr. Khan and Mr. Thiam that ended in Mr. Kahn’s leaving, but he did not elaborate on their relationship. The investigation, he said, did not find any proof the spying was linked to animosity between the two men.

Still, Mr. Rohner apologized, saying that the results of the Credit Suisse investigation “do not change anything about the fact that the reputation of our bank has suffered in the last few days.”

Despite the revelations of the past month, Credit Suisse’s restructuring has had some positive effect on the bank. In the second quarter of this year, the bank’s net profits were 45 percent higher than the year before.

“I am aware that these events were damaging for the reputation of Credit Suisse, but also for the entire financial center of Switzerland, and for this I would like to sincerely apologize,” Mr. Rohner said.