The full writedown of Credit Suisse’s riskiest bonds as part of its takeover by UBS has left some wealthy Asian investors sitting on big losses.

More than $17bn in so-called Additional Tier 1 securities issued by Credit Suisse became virtually worthless last month, following a controversial decision by Switzerland’s financial regulator. Asian high-net-worth investors — including clients of Credit Suisse’s own private bank — were among the holders of these bonds.