ZURICH A group of Credit Suisse AT1 bondholders has filed a class action suit accusing former executives at the Swiss bank, including three past chief CEOs, of being responsible for the bank's downfall.

A lawsuit filed in a New York court on Tuesday accused former bosses Thomas Gottstein, Tidjane Thiam and Brady Dougan, and several other executives of doing excessively risky trades to achieve high short-term returns and bonuses.

"Credit Suisse’s directors and senior executives, and the rotten culture they instilled and fostered, destroyed trust in the bank, which led to its collapse," the lawsuit said.

The lawsuit also accused executives of "creating and perpetuating a culture at Credit Suisse that placed profits, excessive risk-taking, and self-dealing over sound risk management and compliance with the law."

As a part of the collapsed bank's takeover by its former rival UBS in March, Switzerland's regulator decided to render around $18 billion of Credit Suisse's Additional Tier 1 (AT1) debt worthless, which stunned markets and alerted litigators.

The deal upended a long-established practice of giving bondholders priority over shareholders in a debt recovery, triggering hundreds of lawsuits.

Last month, Switzerland’s Federal Administrative Court said it has received 230 claims against the country’s financial regulator FINMA after it wrote off the value of Credit Suisse’s AT1 bonds.

(Reporting by Noele Illien; Editing by Tomasz Janowski)