Spar retailers have united against payment companies Mastercard and Visa after being overcharged for card transaction fees between 2011 and 2015 – one of whom claims to have lost £40,000.

The retail group is in the process of legal action against the card providers. A Spar retailer, who asked to remain anonymous, told RN he has overpaid more than £40,000 in excessive card fees.

“I’ve compared my bills with other retailers and the fees just don’t make sense,” he said. “My charges have reached £40,000 and I’ve been given no reason why my fees are so different.”

Another Spar retailer, who also did not want to be named, added: “I’ve spoken to other retailers and I’ve been charged £400 more in fees. I had no answer when I asked why.”

The card services are provided by merchant Worldpay. Both Spar and Worldpay have confirmed that Worldpay is not part of the legal action.

Spar UK chief information officer Jackie Mackenzie said: “We have joined a consortium of retailers seeking a refund of fees from Mastercard and Visa.

“The litigation relates to losses arising from Mastercard’s multilateral interchanges fees, which form part of merchant service charges Spar retailers have paid banks on card transactions made in store or online between 2011 and 2015.  Spar UK does not comment on any ongoing legal matters and will not be in a position to offer more information to this case until all proceedings are concluded.”

Visa has disputed the claims. “Our interchange rates have been set lawfully at all times for the benefit of consumers, businesses, issuers and acquirers in the UK,” said a spokeswoman.

A Mastercard spokesman added: “We are aware of Spar’s claim and continue to work to highlight the value to those who benefit from electronic payments in the UK.”