Halifax and Lloyds TSB customers have had their cards rejected and been left unable to use some ATMs across the country.
Some customers reported having to leave their shopping behind while others said they have been left unable to access their bank accounts, just before the weekend starts.
Customers have been venting their frustration at the hitches at Lloyds and Halifax, which are part of the same banking group.
A Halifax spokeswoman said the hitches were the result of a "systems failure", which has affected the group's telephone systems as well as ATMs and online services. She said: "The systems are now up and running and we are working through the backlog. The entire backlog will be processed today."
Shopper Marc Dewhurst said he was visiting the Meadowhall centre in Sheffield when he tried to pay using his Halifax card but it was declined, despite him having the cash in his account. He said: "Luckily I had just taken £50 out of a cash machine 15 minutes earlier. I went round to the Halifax and saw people shouting at the staff."
Halifax told customers on its Twitter page that it had been having "intermittent" problems with some of its services. It said: "We're sorry that customers are experiencing problems with some of our services. We're looking into this and will update you as soon as we can."
One Halifax customer wrote: "Card been declined twice this afternoon!! Made to look like a #numpty."
Another Twitter user told the banking group: "Thanks to your 'system error' I have had to use a credit card to withdraw cash!"
It is the latest in a string of banking glitches, following a huge IT meltdown over the summer which meant the accounts of NatWest, Ulster Bank and Royal Bank of Scotland customers did not update properly, causing chaos for many people for weeks. In another separate glitch in July, customers of Britain's biggest building society, Nationwide, saw debit card payments taken from their accounts twice.
Consumer groups have said such problems raise questions about how robust banks' and building societies' systems are.