No less than three French banks have lost money in little more than a year due to controversial trading bets.

Groupe Caisse d’Epargne’s announcement on Friday that it had lost €600m ($807m) after one of its equity derivatives trading teams had overstepped limits and placed risky bets, comes nine months after Société Générale was rocked by a €4.9bn loss, which forced it into a €5.5bn rights issue.