Credit Suisse investment bankers' $700m share of a $5bn toxic asset pool set up in 2008 declined in value in the first six months of this year, a person familiar with the situation said on Thursday.

Credit Suisse took the $5bn worth of assets off its balance sheet in 2008, placing them in a separate vehicle of largely commercial mortgage-backed securities and leveraged loan products in order to scale back risks during the financial crisis.