TSB has apologised for "temporary" problems with its mobile banking app just weeks after IT failures left millions of customers locked out of their accounts.
Customers inundated the bank with complaints on Twitter after being denied access to their money via their phones for several hours on Saturday morning and afternoon.
Users described its service as "consistently rubbish", "absolutely dreadful", "painfully slow" and "broken AGAIN!!" as they vented their frustration.
The bank replied "We're really sorry that some of our customers are experiencing temporary issues with our mobile banking app.
"Customers are still able to access their accounts via Internet Banking using a desktop browser or any mobile device. We're working as hard and as fast as we can to resolve the issue and will update our customers as soon as we can."
Several users said they was considering switching accounts as a result of the problems.
On its website TSB described the mobile app as "intermittent" alongside the same apology.
The bank's chief executive Paul Pester told MPs on the Treasury Committee last month that TSB had lost 12,500 customers in the aftermath of its massive IT failure in April.
Thousands of customers were left locked out of their accounts after TSB moved its customer records to a new banking platform.
Others said they had been able to access other people's accounts and the bank was also overwhelmed by more than 10,600 fraud incidents.
TSB claimed its banking app was "up and running" again by April 25 but some customers were still experiencing disruption in the first week of June.
The bank said it had hired nearly 500 extra staff to deal with the barrage of complaints from customers.
