Lloyds Banking Group has apologised after an IT glitch left customers unable to withdraw cash from ATMs on Sunday afternoon
The technical fault hit Lloyds, TSB, Halifax and the Bank of Scotland - all of which are owned by Lloyds Banking Group.
Cash machines were faulty for four and a half hours and debit card transactions were disrupted for three hours before the problems were eventually resolved.
A spokeswoman for the group said: "Although the majority of transactions were unaffected, we are very sorry for the inconvenience that this will have caused.
"At the same time, some customers encountered problems at approximately half of our 7,000 ATMs. This was resolved by 7.30pm, and all of our ATMs are now working."
Online and telephone banking were unaffected by these issues, and customers were still able to withdraw cash from other ATMs.
TSB chief executive Paul Pester said in a tweet that hundreds of people were queuing to talk to customer services about the issue.
"At one point we had 300 customers queuing to speak to the call centre - sorry if you couldn't get through," he said.
He added last night: "The cause of the problems at TSB is now fixed. It'll take a while to sort the backlog.
"Thanks to all TSB colleagues who worked so hard this afternoon to fix the IT issues. Sorry once again to all our customers affected."
He blamed the problem on a "server failing" in the UK and confirmed all brands under Lloyds Banking Group were affected because they share the same IT system.
Disgruntled customers took to social media to express their dissatisfaction.
Carl Bullivant tweeted: "Wife's card declined in Asda had to go get my card from home how embarrassing standing and waiting £poorbankingservice."
Essie Young wrote: "Didn't even want to be a @TSB customer when LTSB split! Couldn't buy my twins bday presents today with TSB card! £fuming £customerservice."
Another customer tweeted: "@TSB left me unable to pay for my shopping and no access to my money. TSB are a joke."ATMs are now working."
Additional reporting agencies