Britain's Lloyds Banking Group suffered an outage on Wednesday that left customers of its Lloyds, Halifax and Bank of Scotland operations unable to access their accounts online.
Disruption to online services is a periodic problem for Britain's banks, and last month regulators told lenders that they needed to boost their ability to resolve problems swiftly.
Customers of Lloyds Banking Group said on social media that they were unable to use the bank's mobile apps or websites to access their accounts on the first day of 2020, a public holiday in Britain when bank branches are shut.
"We know our customers are having issues with internet and/or mobile banking. We're sorry about this and we're working to have it back to normal soon," the group said in a statement.
The problem has been going on for several hours and a spokeswoman said she did not have any information on how soon it would be fixed or how many account holders were affected.
Customers of TSB, a lender owned by Spain's Sabadell , suffered weeks of disruption in 2018 due to an IT failure that drew criticism from parliament and regulators and ultimately forced its chief executive, Paul Pester, to resign.