The Qatar Investment Authority (QIA), the country's sovereign wealth fund, has become the second-largest shareholder in Credit Suisse after doubling its stake in the embattled Swiss lender late last year, according to a filing with the US Securities and Exchange Commission.

QIA initially began investing in Credit Suisse around the time of the financial crisis. Now, it owns 6.8% of the bank's shares, according to the filing on 20 January.

This puts the QIA in second place to the 9.9% stake purchased by the Saudi National Bank last year as part of a $4.2bn capital raise to fund a big strategic overhaul.

Combined with the 3.15% owned by Saudi-based family firm Olayan Financing Company, around 20% of the company's stock is now owned by Middle Eastern investors, according to Eikon data.

In December last year, the Wall Street Journal reported that Saudi Arabia's Crown Prince Mohammed bin Salman was preparing to invest in Credit Suisse's investment bank, while other investors could include former Barclays chief executive Bob Diamond.

Prince Mohammed may invest around $500m in the lender's CS First Boston spinout, the newspaper said, citing people with knowledge of the matter. He has been encouraging Saudi Arabia's largest firms to expand globally, raise the country's profile as a serious investor and diversify its economy.

According to a report at that time in the Sunday Times, Diamond, who is chief executive of Atlas Merchant Capital, was understood to be in the early stages of looking at providing capital and operational expertise to CS First Boston. 

Credit Suisse will initially hold a controlling stake in New York-based CS First Boston but it wants to bring in third party investors with the aim of exiting through a stock market listing in five years' time.  

Credit Suisse will report its fourth-quarter and full-year earnings on Feb. 9, and has already projected a 1.5 billion Swiss franc ($1.6 billion) loss for the fourth quarter.