The issues started over the weekend with many customers unable to pay for groceries by card, while others were charged twice.

ACI manages payment transactions for both stores. It said it was working “as quickly as possible” to fix a problem affecting card payments.

Customers of both supermarkets have taken to Twitter to complain.

One Twitter user said: “@Morrisons I’ve got a transaction problem. I was in the store yesterday and have paid for the same shop twice as there was a problem with the card machines and it’s been taken from my bank twice. Please can somebody DM me.”

Another Tweeted: Just been into @Morrisons – wish I hadn’t, all tills down, all contactless cards not working #chaos queue for self-service, didn’t work, then told to take receipt to tobacco kiosk, didn’t work, then realised I had #CASH! No problemo. That’s why we MUST keep cash in the system.”

Gareth Shaw, Which? head of money said: “This was a concerning situation for shoppers and reinforces why cash is such a vital back-up when technology fails – even for those who prefer to use digital payments.

“A reduction in retailers accepting cash during the pandemic has combined with widespread bank branch and cash machine closures to push the UK’s already fragile cash system even closer to the brink of collapse.

“To avoid cutting off millions of people from their preferred payment method, the government must urgently introduce the legislation promised in last year’s budget and the industry must commit to supporting the existing cash network until a new system is in place.”

A statement from ACI worldwide said: “Customer relationships and the stability of our systems remain an absolute priority for ACI Worldwide. We are working closely with the IT teams at our partners to resolve the problem as quickly as possible. We apologize to shoppers for any inconvenience caused.”