Santander is to close 140 branches, putting 1,270 jobs at risk, the bank announced on Wednesday.
The company is in talks with unions to try to find new roles for staff affected where possible and said it expects a third to be redeployed.
Customers will be supported in finding alternative branches and other ways to bank, Santander said.
The bank blamed a 23 per cent fall in the number of transactions in branches over the last three years, during which time digital transactions have almost doubled.
UK banks closed 757 branches last year and in January 2019, according to Which? figures. The number of cash machines has also dropped sharply, particularly in rural areas, raising concerns that many consumers are being denied access to financial services.
Susan Allen, head of retail and business banking, said: “The way our customers are choosing to bank with us has changed dramatically in recent years, with more and more customers using online and mobile channels.
“As a result, we have had to take some very difficult decisions over our less visited branches, and those where we have other branches in close proximity.
“We will support customers of closing branches to find alternative ways to bank with us that best suit their individual needs.
“We are also working alongside our unions to support colleagues through these changes and to find alternative roles for those impacted wherever possible.
“We continue to believe that branches have a vital role to play and we will be refurbishing 100 of our branches over the next two years. We are confident that following these changes we will have the right branch network to serve our customers’ changing needs, and we expect the size of our network to remain stable for the foreseeable future.”