More banks could see their contingent convertible (CoCo) bonds downgraded, Standard and Poor's has warned, a week after Deutsche Bank's bonds were targeted by the credit ratings agency. The price of the risky bonds has crashed by as much as 25pc in recent weeks as a wave of fear swept the market, with investors panicking that Deutsche Bank could struggle to pay the interest coupon on the bonds. The bank insisted that it has plenty of liquidity available to service its debts and bought back almost €5bn (£3.9bn) of senior bonds to illustrate the point. Since then Deutsche Bank's CoCos have shown some signs of rebounding.