(Reuters) – Credit Suisse creditors holding more than 4.5 billion Swiss francs (4.59 billion euros) in Additional Tier 1 (AT1) bonds have filed a complaint against the Swiss Financial Market Supervisory Authority (FINMA), the Swiss stock market policeman.

As part of the emergency takeover of the bank by its rival UBS at the end of March, the Swiss authorities decided that the value of the AT1 securities of Credit Suisse would fall from 16 billion francs to zero, angering some holders of the debt who thought they were better protected than the shareholders in the event of a rescue procedure for the establishment.

The lawsuit, which was filed on April 18 by law firm Quinn Emanuel Urquhart & Sullivan, challenges FINMA’s decision on the impairment, the firm said on Friday.

“FINMA’s decision undermines international confidence in the legal certainty and reliability of the Swiss financial center,” Thomas Werlen of the law firm said in a statement.

FINMA declined to comment on the lawsuit. Credit Suisse did not immediately respond to a request for comment from Reuters.

(Jahnavi Nidumolu and Jyoti Narayan report in Bangalore; Blandine Hénault for the , edited by Bertrand Boucey)

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