Santander’s telephone, branch, online, ATM and card services all experienced major issues on Saturday.

The problems left customers locked out of their accounts, unable to make card payments, and unable to withdraw cash from Santander ATMs. Many took to social media to express their frustrations.

Santander Tweeted about the issues on Saturday morning, before Tweeting updates in the afternoon, advising customers to withdraw cash from other banks’ ATMs.

A statement on Santander’s website on Monday morning apologised for the issues over the weekend and said all services were back up and running.

The statement said: “Our banking services continue to run as normal, with our branches, call centres and chat service available as usual, however it may take longer to get through on the phone. We appreciate your patience.

“We want to make sure no customer is out of pocket, so we will confirm how you can request reimbursement if you have incurred costs because of these issues as soon as possible. We’ll publish full details on our website, on our Facebook page and on Twitter. Once again, we are very sorry for the inconvenience this has caused.”

Gareth Shaw, head of money at Which?, said: “These technical issues will be causing stress for many Santander customers – with people reporting that they have been unable to make online payments or in some cases purchase food in their local supermarket.

“Customers can incur fines, penalties and fees when they’re not able to access their finances, so the bank must offer compensation to all those who have been impacted in this way. These problems demonstrate why it is vital that banks invest to ensure their systems are up to the task of protecting their customers’ accounts and maintaining the services they rely on.”