Shoppers at Sainsbury’s, Waitrose, Homebase, Argos and B&Q were unable to pay by credit or debit card during Saturday afternoon, following a payment processing glitch at Barclaycard.

The problem lasted for around 20 minutes from 2.15pm, according to Barclaycard, which blamed a “computer error” affecting its electronic fund transfer system that processes payments for the stores. The company said it is still investigating exactly what went wrong.

Barclaycard IT glitch hits shoppers at Sainsbury'sThe news came days before parent group Barclays said it was outsourcing its credit card and payment business operations to Indian business process outsourcing firm FirstSource from 1 November. FirstSource will take over Barclaycard’s payment servicing team in Merseyside and a customer contact centre in Teesside.

A spokesperson at Barclaycard had not explained how many roles would be affected at the time of writing. But Derek Allgood, global sales and service director at Barclaycard, said in a statement that Firstsource had made a “commitment to establish a long-term presence” at the Teesside site.

Saturday's payment system outage hit all of Sainsbury’s 872 stores, the supermarket told the BBC. B&Q  and other stores are understood to have switched to manual card transaction terminals to continue with payments.

It is not known how many other retailers were affected. Barclaycard processes payments for 85,000 UK retail outlets.

As queues formed at cashpoints with people attempting alternative methods of payment, customers expressed their frustration on Twitter.

One warned of “big queues” at Sainsbury’s, adding: “Make sure you bring cash!”. Another, shopping at Waitrose, said: “One machine broke, they took out all the others and are only accepting cash.” Others described the “chaos” and “bedlam” at the stores.

Barclaycard apologised for the problem in a statement, adding: “For about an hour on Saturday afternoon, we experienced a technical issue that meant card payments could not be made in some large retailers.” It said it had begun a “thorough investigation” into the cause.

Two months ago, Barclays experienced another glitch that left customers unable to use their credit or debit cards, unable to use cash machines and unable to access their online accounts.

In the last four years, Barclays has offshored more than 2,400 back office jobs to its own locations and outsourcing firms overseas, with 71 percent of operational sites closed in the last four years. The reduction in the number of sites was delivering “smoother, faster processing”, Barclays claimed.