The crisis at IKB, the German bank crippled by its subprime investments, claimed one of its biggest casualties on Monday when the chief executive of the bank’s largest financial backer resigned.

Ingrid Matthäus-Maier said she was stepping down on health grounds as the head of the management board at KfW, the state-owned development bank. KfW said its role in the multiple bail-outs of IKB had cost it €7.2bn ($11.3bn).