Barclays is to slash 1,700 staff across its UK branches, stating that increasingly customers access their services using smart phones and through other technology.
The bank warned its employees that frontline roles, including cashiers, personal bankers and operational specialists, will be cut throughout 2014.
Barclays, which has 1,577 branches in the UK employing 33,600 staff, said the way in which its customers access their banking services is changing rapidly and the lender is to invest more in its infrastructure.
"As a result of technological changes, we will be able to provide better service for our customers with fewer staff in our branches," a spokesman for Barclays said. "We have outlined a voluntary redundancy scheme for those colleagues who are interested."
But trade union Unite, which represents staff at Barclays, branded the move as a "colossal mistake", warning that customer service could suffer as a result.
"It's a colossal mistake for Barclays Bank to announce 1,700 job cuts across its bank branches," said Dominic Hook, Unite national officer.
He added: "These employees deliver high levels of service that customers of the bank benefit from. Such a massive reduction will be very detrimental to the bank and will also be hugely challenging for the staff remaining."
The announcement follows news of Coventry and Dartford centres closing down - culminating in 600 job losses.
Workers at the Coventry site were told that the call centre is to be closed in June 2014.
Unite claimed the move means 350 jobs will be lost and that the majority of job losses will be amongst those in the call centre earning up to £17,500 ($28,147, € 20,908).