NatWest and RBS customers have fired off a volley of complaints following a two-day breakdown in service from the bank's mobile apps.
The outage follows a routine upgrade to the banks' online services over the weekend.
The Twitter service team @natwest_help have been busy apologising to customers who have used the micro-blogging service to express their frustration with the ongoing problems.
The degree of anger expressed by customers over the glitch demonstrates the booming popularity of mobile devices for accessing banking services. According to the British Bankers’ Association, the number of mobile banking transactions has soared over the past year, with smartphones and tablets used for 18.6 million transactions a week.
In a statement e-mailed to Finextra, NatWest says: “We are aware that some customers are experiencing difficulty accessing our mobile banking. We’re investigating this and we are working to get it resolved as quickly as possible. In the meantime our customers can visit one of our branches, use online banking or call us via telephone banking as normal. We apologise to customers for the inconvenience."