The settlement agreed earlier this month was designed to end a seven-year legal dispute over interchange fees, with retailers securing a multi-billion dollar cash payment and significant reforms of Visa and MasterCard rules and business practices.

However, in a statement, Walmart - America's biggest retailer - says that it, along with other merchants and consumer groups, is "disappointed" in the deal, arguing it would "not structurally change the broken market or prohibit credit card networks from continually increasing hidden swipe fees, which already cost consumers tens of billions of dollars each year".

With the settlement requiring merchants to waive their rights in actions against the card networks and constraining emerging payments innovation, Walmart "encourage all merchants to put consumers first and reject the settlement".

Walmart's rejection of the deal echoes a similar statement from its rival, Target, which said last week that the "proposed settlement would perpetuate a broken system, restrict retailers from any future legal action and offer no long-term relief for retailers or consumer".