Lachappelle, a lawyer, has been chief executive of Basler Kantonalbank since 2013.

"Guy Lachappelle is a very experienced banker who identifies with Raiffeisen's cooperative values and has successfully proved himself in transformation processes," Deputy Chairman Pascal Gantenbein said in a statement.

Lachappelle said he was honoured to be chosen to head the lender through what he called challenging times.

"Given my previous activities and experience I feel well prepared to take on the chair of an organisation about to make important decisions," he said.

Financial market supervisor FINMA said in June it had found serious breaches at Raiffeisen in a probe related to fraud allegations against former CEO Pierin Vincenz.

It told Switzerland's third-largest bank, which is owned cooperatively by 1.9 million customers and is not listed, to conduct a detailed analysis of converting into a limited company, a step that could improve corporate governance.

Prosecutors are investigating Vincenz, who denies wrongdoing but has been forced to resign, on suspicion of breach of trust linked to cashless payments business Aduno as well as private equity firm Investnet.

Raiffeisen proposed four new supervisory board members, including Thomas Mueller, chief risk officer at EFG International.

(Reporting by Michael Shields; editing by Jason Neely)