Credit Suisse has become the latest Western financial institution to be targeted by a sovereign wealth fund after the Qatar Investment Authority bought a stake in the Swiss investment banking and wealth management group as part of plans to invest about $15bn in US and European banks.

The QIA acquired its holding in the stock market, in contrast with other sovereign funds that have bought fresh equity in troubled financial institutions, diluting existing shareholders. The stake is believed to have cost no more than $500m, and amounts to between 1 and 2 per cent of the bank.