The Unite union, which represents many Barclays workers, says the bank's decision to cut up to 1,700 jobs is 'a colossal mistake'.
The union said frontline roles, including cashiers, personal bankers, operational specialists, branch managers and assistant managers will go throughout 2014.
It claimed that customer service would be affected by the changes and said Barclays risked damaging its reputation.
In a statement Barclays said fewer of its customers were using branches.
Barclays bank says changes in the way customers use its branches is behind the decision to cut up to 1,700 jobs.
In a statement it said that new technology meant that fewer everyday transactions were now done in high street branches.
The bank said it would provide a better service with less staff.
It has started a voluntary redundancy scheme.
– Barclays statement
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.
As a result of technological changes, we will be able to provide better service for our customers with fewer staff in our branches.
Barclays is to axe 1,700 jobs from across its branch network, according to the Unite union.