Japanese investors sue Switzerland over Credit Suisse's AT1 write-down, law firm says

ZURICH, Dec 4 (Reuters) - A group of Japanese investors has sued Switzerland over write-downs of Additional Tier 1 (AT1) hybrid bonds of fallen lender Credit Suisse, law firm Drew & Napier, which represents them said on Thursday.

The 184 investors filed an arbitration request with the International Centre for Settlement of Investment Disputes, or ICSID, claiming Switzerland violated a free trade agreement with Japan when wiping out the bonds in March 2023.

The Swiss government did not immediately reply to a Reuters request for comment.

Swiss market regulator FINMA wrote off 16.5 billion Swiss francs ($20 billion) in AT1 bonds during the state-engineered takeover of Credit Suisse by rival UBS, triggering investor backlash and legal challenges in Switzerland, the U.S., and investor-state arbitration under bilateral treaties.

A Swiss court ruled in October that the write-off was unlawful, boosting bondholders' hopes of recouping losses and raising fresh questions about how authorities handled the crisis.

The court said that around 3,000 complainants lodged appeals with it over FINMA's decree in about 360 cases.

The Japanese investors argue Switzerland treated them unfairly, arbitrarily and without due process, and that they were effectively expropriated, according to Drew & Napier.

The firm did not specify the size of the claim but said that, overall, it represents around 560 Asian bondholders across Japan, Hong Kong and Singapore, with total claimed losses exceeding $300 million.

The firm also said that further filings with the ICSID arbitration court were expected in the coming months.

($1 = 0.8007 Swiss francs)

(Reporting by Ariane Luthi; Editing by Ludwig Burger)