Barclays customers were left unable to make payments using their cards after its digital services experienced "technical difficulties".
ATM machines were affected, while people also reported problems using cards in shops.
Telephone banking and in-branch payments are also thought to have been hit.
The problem was not down to a cyber attack but because of issues with the bank's own systems.
ITV News Consumer Editor Chris Choi said the situation was a "fiasco" for Barclays.
Barclays tweeted on Saturday: "Technical issues are affecting some digital services. We're investigating this and apologise for any inconvenience."
It later added: "We're still experiencing issues affecting Barclays Debit Card and ATM transactions. Our teams are working to get this restored."
Customers were left fuming after discovering they could not use their cards.
One posted on Twitter: "Got stuck in a car park with my little boy because I was unable to pay my ticket. Some lovely lady helped me out and paid for it".
Another said: "Just had to tell my tattoo artist I couldn't pay him half way through. Now in the pub for dinner but guess what?"
Barclays said the problem was fixed by 4.20pm. It did not know how many customers were affected.
A spokeswoman said: "We're aware some customers may have had issues with some digital services today.
"We can confirm everything is now back up and running and customers can get money out of ATMs and card payments are going through.
"We apologise to any customers that were impacted."