Credit Suisse today suspended a group of traders allegedly responsible for a $2.85 billion (£1.5 billion) write-down that will wipe at least $1 billion off the Swiss bank's profit in the first quarter and potentially alter its results for 2007.

The team, led by Kareem Serageldin, the bank's global head of synthetic collateralised debt obligations (CDOs), which are a type of complex financial instruments, are still employed by Credit Suisse. But a number of trades are now a subject of an internal investigation at the bank.

Credit Suisse declined to comment on the traders' identities.

Speaking earlier today, Brady Dougan, chief executive at Credit Suisse, said traders had been "tardy" in the repricing of complex financial products which contributed to today's shock $2.85 billion writedown.

The “mismarkings and pricing errors” in Credit Suisse’s Structured Credit Trading division, which operates from London and New York, were discovered last week after the bank announced its fourth quarter and full-year results on February 12.

It reported a full-year profit of SwFr8.5 billion and reduced its sub-prime mortgage-linked writedown by SwFr200 million.

In marked contrast, rival UBS made its worst-ever loss of SwFr4.4 billion for the year as sub-prime writedowns reached $13.7 billion.

Mr Dougan said today that the "mispricing" was an isolated incident and contributed only a small amount to the overall writeoff, with the value of assets falling due to adverse market conditions.

The bank denied the situation is akin to the trading scandal enveloping France’s Société Générale, and at this stage fraud is not suspected. An internal review is continuing at the bank.

Today's admission arrives at a critical time for Credit Suisse which is the subject of investment by the Qatari Investment Authority (QIA), which attempted, and failed, to buy J Sainsbury last year. It is believed the QIA has acquired less than 3 per cent in the Swiss bank.

The bank said it expects the writedown to impact net profit by $1 billion in the first quarter.

However, it conceded the final figure could differ from today's estimate depending on "further results of our review and continuing market developments".

It added: "We will also assess whether any portion of these reductions could affect 2007 results."

Shares in Credit Suisse plunged by 9.3 per cent to SwFr51.45 after shocked investors digested today's announcement which was made as the bank launched a new $2 billion bond due for repayment in 2018.

Credit Suisse will determine whether the trading mistakes have affected last year’s results when its accounts are finalised in March.

A spokesman at Credit Suisse declined to comment.

Commenting on the bank's fourth quarter and full-year results, Mr Dougan said: "Our integrated business model, global reach, strong risk management capabilities and capital position proved important competitive advantages, as we delivered year-on-year growth and sustained profitability."

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