Barclays is to axe 1,700 jobs throughout 2014, the bank announced today.
Unite, the union representing Barclays staff, called the move a “colossal mistake”.
The jobs lost will be branch-based roles, from cashiers to managers. The union has warned customer service will be damaged by the cuts, but the bank disputes this.
A Barclays spokesman said: "The way in which our customers access their banking services is changing rapidly.
"More and more people are choosing to use smartphones and technology for everyday transactions - using branches only when they need access to expertise.
"We are responding by investing in the channels that customers are increasingly using, whilst improving customer service."
Unite national officer Dominic Hook said: "It's a colossal mistake for Barclays Bank to announce 1,700 job cuts across its bank branches.
"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.
"Unite is pressing Barclays to reconsider this proposal for the sake of its reputation for high customer service. Consumers want to engage with knowledgeable, highly experienced, professional staff. By taking 1,700 of the workforce away, Barclays risks massive reputational damage."