Plea comes as ministers and central bank chiefs of G7 powers discuss subprime crisis.
Unlike the Swiss bank UBS, which has been hit by $18bn of charges, and some major US banks such as Citigroup and Merrill Lynch, Credit Suisse had until now been relatively unscathed by the credit crisis.
“Those who thought that certain banks such as Credit Suisse were ‘out of the woods’ should exercise caution,” said Chris Wheeler, a banking analyst at Bear Stearns.
Credit Suisse said the charges reflected “significant adverse first-quarter 2008 market developments”.
The bank said the write-downs would wipe $1bn from its first-quarter net income, after taking into account tax credits and cancelling some staff bonuses, but it still expected to stay in profit in the quarter, despite the charge.
However, a spokesman for Credit Suisse said he was unable to quantify the impact of the errors and mismarkings on the size of the write-downs.
The revelations were particularly embarrassing for Credit Suisse because the bank had only recently shaken off a reputation for being accident-prone and springing unpleasant surprises on investors after completing a painful restructuring.
“This is very disappointing for Credit Suisse, who only last week produced their 2007 results and bragged how successful they were in comparison with other banks,” said Thorne.