Crédit Agricole, France’s largest retail bank, last night announced a surprise €2.5bn ($3.6bn) pre-tax writedown in a move that will leave its Calyon investment banking arm in a clear loss. Financial Times

George Pauget, chief executive, said events in recent days had prompted management to review provisions against Crédit Agricole’s exposure to the subprime crisis.

Including provisions taken in August and September, France’s biggest retail bank has now taken a €3.3bn hit in 2007 to cover the possible consequences of the crisis.

The group also decided to write down the value of its super-senior CDOs, in accordance with recent guidance from the International Accounting Standards Board.