Crédit Agricole has lost its two most senior investment bankers with the surprise resignations of Dominique Ferrero and Marc-Antoine Autheman.

The sudden departures, announced on Monday evening after a meeting of Crédit Agricole's board, highlighted the difficult task of integrating Crédit Lyonnais, which was acquired by its rival for €19.5bn ($24bn) last summer after a four-year courtship and a short-lived bidding battle with rival BNP Paribas.