Online bank Smile is trying to reassure customers after days of technical problems with its website and app.
On Wednesday, Smile – which is owned by Co-op Bank – said on Twitter that it was having “intermittent issues with our app and online banking”.
The bank’s 100,000 customers were given a phone number to call during daytime hours for help.
But there were still problems on Friday, and a spokesperson told Sky News: “We’re sorry that our Smile customers have been unable to use our mobile app and online banking as they would usually in recent days.
“We are working hard to restore their access as soon as possible and we apologise for any inconvenience caused.
“Customers can use their cards and make transactions as normal and if they need support with their account they can call our customer service team.”
Cards can still be used for transactions or at ATMs, and direct debits are still being paid, the bank added.
Customers were not impressed, with Lucas Jedrzeiak tweeting: “There’s nothing to ‘smile’ about! Many frustrated but loyal customers are thinking of leaving you.”
Another, Gareth Wyatt, wrote: “You can’t be an online bank that’s never actually online. This is beyond ridiculous.”
Smile, which started as the UK’s first fully digital bank in 1999, is not the first to face thousands of angry customers over an IT meltdown.
RBS was fined £56m for failures linked to IT issues in 2012, which left more than 6.5 million customers across the group without access to their money for several weeks.
And TSB Bank lost 80,000 customers after an IT problem that left around 1.9 million people unable to access their accounts in 2018.