Brussels, 30/10/2003 (Agence Europe) - The MasterCard bank card group should justify its invoicing methods to the European Commission, more specifically the commissions charged by the group to perform electronic transfers between the retailers banks and those of customers. In fact the European executive confirmed the sending of warning letters on this matter, having noted that retailers were forced to pay disproportionate prices to use the payment system. We are concerned by the high fees between banks, which are not transparent and extremely high. Even if prices have increased over time, no choice has been offered for other payment systems, stated the spokesperson Tilman Leuder. This investigation will enable the Commission to check whether MasterCard does not use a strong position in the market to maintain excessive commissions. MasterCard now has the possibility of requesting an oral hearing to outline its defence.