INVESTORS representing more than 4.5 billion Swiss francs (S$6.7 billion) of Credit Suisse bonds have sued the Swiss Financial Market Supervisory Authority (Finma) over its decision to wipe out their investments in last month’s emergency government-orchestrated takeover.

Law firm Quinn Emanuel Urquhart & Sullivan, which is representing the bondholders, said on Friday (Apr 21) that the move was the first in a series of steps to seek redress for its clients. It added that the bondholders had been unlawfully deprived of their property rights during Credit Suisse’s takeover by bigger rival UBS.

This is the first major lawsuit in the public domain to be filed over the Swiss decision to wipe out around US$18 billion of Credit Suisse’s Additional Tier-1 (AT1) debt in the three-billion Swiss franc all-share rescue deal, which stunned markets and alerted litigators.

The appeal against Finma, the agency that ordered the write-down, was filed on Tuesday in the Federal Administrative Court in St Gallen, north-eastern Switzerland.

“Finma’s decision undermines international confidence in the legal certainty and reliability of the Swiss financial centre,” said Thomas Werlen, Quinn Emanuel’s Swiss managing partner.

“We are committed to rectifying this decision, which is not only in the interests of our clients but will also strengthen Switzerland’s position as a key jurisdiction in the global financial system.”

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Finma declined to comment; Credit Suisse did not immediately respond to a Reuters request for comment.

Last month, Finma said its decision to impose steep losses on some bondholders was legally watertight because the bond prospectuses and emergency government legislation allowed for a total write-down in a “viability event”.

Engineered in the wake of the global financial crisis, AT1 bonds were designed to ensure investors, not taxpayers, carry the burden of risk if a bank runs into trouble.

Bondholders have been seeking legal advice since the rescue upended a long-established practice of prioritising bondholders over shareholders in debt recovery.

A number of claims have already been filed in Switzerland over the terms of the deal.

The Federal Administrative Court said it is still receiving complaints, but declined to name claimants or comment on how many have been lodged by bondholders or their lawyers.

Some investors have been trading the notes at penny prices in a so-called litigation play, betting that successful legal claims will boost values in the future, lawyers have said. REUTERS