Cutbacks at RBS and NatWest were blamed yesterday for a technical glitch that left customers unable to use their debit and credit cards on Monday.

The embarrassing failure, which left some unable to pay after filling up with petrol or to settle restaurant bills, and in other cases forced them to abandon full shopping trolleys, was the latest in a string of system meltdowns for the RBS-owned group.

It came on so-called Cyber Monday - the day online retailers expected the most sales to take place before Christmas.

The glitch also affected the banks' websites.

"The systems issues that affected our customers last night have now been resolved and all of our services are now back working normally," said the group.

"We would like to apologise to our customers.

"If anyone has been left out of pocket as a result of these problems, we will put this right," the group added.

A previous IT failure in May left RBS and NatWest customers using mobile apps unable to access their accounts online.

It followed a major fiasco in June 2012 that saw payments go awry, wages appear to go missing and home purchases and holidays interrupted - costing the group £175 million in compensation.

Unite, which represents staff at RBS, called on the bank to halt its deep spending cuts.

Since 2008 the group has axed over 30,000 jobs in Britain and started an internal shake-up that includes moving IT work abroad.

Unite challenged the bank to prove that the latest problems were not caused by staff shortages or a lack of spending and investment on its core infrastructure.

National officer Dominic Hook said: "Questions must be asked as to why constant job cuts are being made when there are clearly serious issues which need addressing by management.

"Customers and staff have the right to expect more from their bank."

RBS, which is 80 per cent owned by the taxpayer after being rescued during the financial crisis, has also been criticised in the past week over allegations that it drove distressed firms to collapse so it could buy their assets at rock-bottom prices.