HSBC has alerted customers to "intermittent issues" affecting mobile banking services in a social media post, while TSB's long-suffering customers are yet again finding themselves locked out of online and mobile banking after months of IT problems at the bank.

The latest glitches follow a series of outages which hit Barclays, RBS, Natwest and Ulster bank last week.

With neither TSB or HSBC providing a timeframe for fixes to the current spate of issues, software architecture firm Cast is calling for an urgent review into the resilience of UK bank systems, especially during heavy-use periods such as the the end of the month.

“Banks in other geographies don’t have as many problems as UK banks," says Lev Lesokhin, SVP strategy & snalytics at Cast. "Based on our research, UK-serving banks such as HSBC and TSB don’t do as good a job controlling the structural quality of their legacy systems. Software is a product of many software developers across geographies and vendors, particularly the case with international banks such as HSBC. Making sure their product is actually reliable is something that’s currently largely left to chance. This is why we’re in a situation where banking software fails us so regularly."

At a time when banks are closing more branches and bolting on new digital banking services to legacy architecture in a race to keep up with greenfield startups, the resilience of the sector to IT failures has become a major concern for regulators.

In July, the Bank of England and financial watchdog the FCA gave British financial firms a three-month deadline to demonstrate their operational resilience in the event of a cyber attack or IT breakdown. Penalties for those firms that fail to demonstrate adequate planning could result in a requirement for higher capital levels, sanctioning of executive leadership and a demand for more IT investment.