The Madrid-based bank's UK business said it would close 140 branches across the country, leaving it with 614.

The closure programme will lead to around 840 redundancies, with the bank expecting to be able to redeploy only a third of the 1,270 staff affected.

Santander said it had consulted with trade unions on the proposed changes and would try to find alternative roles for staff where possible.

Santander's action marks the latest round of major branch closures by British high street banks.

Britain has lost nearly two-thirds of its bank and building society branches over the past 30 years, according to research by consumer campaign group Which? published in November. The number of branches at that time stood at 7,586, down from 20,583 in 1988.

Santander said it was making the changes in response to the rapid uptake of digital banking. It said the number of transactions carried out in branches had fallen by 23 percent over the past three years.

It will invest 55 million pounds ($71.36 million) in refurbishing around 100 of the remaining branches.

Linda Rolph, general secretary of the Advance union, which represents Santander workers, told Reuters: "It is a sad day for the branch staff affected. We will do everything we can to find jobs for people who want them."

Rolph said the union was not resisting the changes: "Santander was one of the last to move to cut branches. We're not opposing because the rationale is clear. Staff thought it was a matter of time before some branches closed."

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."