U.S. shareholders are bringing a class-action suit against Credit Suisse – and against Chief Executive Tidjane Thiam. 

The catalyst for the suit appears to be roughly $1 billion in write-downs in 2015 and 2016, shortly after Tidjane Thiam took over at the helm of Credit Suisse, Swiss weekly «Sonntagszeitung» (in German) reports. The Zurich-based bank had taken the hefty write-down due to illiquid financial instruments.

The lawsuit represents a late denouement of Thiam's first big snafu at Credit Suisse, in which he further muddied the waters by claiming senior bank executives hadn't been informed of the losses. The losses eventually led to the ouster of investment bank head Tim O'Hara the following year.

CS Hits Back

The plaintiffs assert that Credit Suisse misled shareholders and the public over the  risky assets, hiding the truth from its investors. Credit Suisse denied the allegations.

«The claims are baseless and without foundation. In the last three years, Credit Suisse has evaluated the allegations and fulfilled regulatory requests for information. All regulatory evaluations have been concluded without any sanction against Credit Suisse,» the bank said in a statement.

«At All Costs»

According to «Sonntagszeitung,» the plaintiffs, including a pension fund of Birmingham, AL's emergency services, question that Credit Suisse's management didn't know of the illiquid assets. They allege that top executives should have known, or could easily have gained the information.