By Emma Rumney and Lawrence White
(Reuters) - Royal Bank of Scotland
RBS said it is working to fix problems with its online and mobile banking services on Friday, following similar outages on Thursday that hit Barclays
RBS and Barclays are set to face calls from lawmakers on Britain's Treasury Select Committee to explain what caused the problems, a source familiar with the matter told Reuters on Friday, following similar inquiries into the failings at Cashplus this week.
The outages come when Britain's lenders have been driving customers towards such services as the banks cull branch networks to cut costs. Regulators and politicians are increasing scrutiny over banks' cyber resilience.
Royal Bank of Scotland Chief Executive Ross McEwan told LBC Radio that the outage may be related to regular changes it had made to its technology, such a change to its firewall, but the cause was not clear yet.
"The team are working flat out… We feel the pain for our customers every time this happens," he said.
The RBS outage on Friday also affected NatWest, RBS's most highly rated brand among customers. The lender used Twitter to apologise to customers and said telephone banking and ATMs were working as normal.
Numerous customers took to social media to complain about the outage.
"So how do you expect me to pay my bills today when I work 9-5," Natalie Wilkinson said in a tweet to NatWest, asking other users to recommend a more reliable bank.
The consequences for banks of online banking problems and the subsequent scrutiny of those failings by politicians can be severe.
Earlier this year a major outage at mid-sized lender TSB, owned by Spain's Sabadell
TSB Chief Executive Paul Pester resigned this month, following heavy criticism by the Treasury Committee and the bank's customers for his handling of the crisis.
British banks do not have long to strengthen their contingency plans for when online banking services fail.
The Bank of England and the Financial Conduct Authority in July set a deadline of Oct. 5 for British lenders to explain how they can avoid damaging IT breakdowns and respond to the growing threat of cyber attacks.
(Additional reporting by Shubham Kalia in Bengaluru; Editing by Kirsten Donovan and Keith Weir)