Credit Suisse's chief operating officer Pierre-Olivier Bouée resigned after an internal probe found he ordered the surveillance of the bank’s former wealth management chief by private investigators without discussing it with chief executive Tidjane Thiam or other senior bank officials.

His decision set off a scandal that has enveloped the bank for the past two weeks, triggering an internal investigation at Credit Suisse and dealing one of the more unusual challenges that Thiam has faced at the bank.