Barclays staff are "alarmed" by plans to close a quarter of the bank's 1,600 branches in the UK under moves to slash costs, according to a leading union.
The bank refused to comment on reports of a jobs cull, but Unite attacked the "reckless rush" to close branches, which it warned would be unpopular with customers.
The union published a survey earlier this week which showed public opposition to automation in bank branches, with consumers preferring to deal with staff rather than machines.
Dominic Hook, Unite national officer, said: "Staff at Barclays are alarmed by the plans announced today. There is no justification for such proposals. Barclays must not embark on this reckless rush to close branches and fill others with machines instead of staff.
"There will be a significant cost to customer service in Barclays. Unite has called on Barclays to halt their bank branch closure plan. The banking industry must step back from the rush to install banking machines across all their branches at the continued expense of employment and training of a much-valued workforce.
"Research shows the significant reputational damage the banks will suffer if they ignore the needs of their customers. With 72% stating they have had problems with machines in branches and 62% preferring more staff in branches, there is no doubt about the importance of frontline bank staff.
"Barclays customers don't want to see empty soulless branches. There are serious questions as to what this reduction in staff numbers will do to customer service in Barclays."
Speculation over Barclays' branches follows an announcement yesterday by Lloyds Banking Group of 1,080 job losses across its retail, risk, operations and commercial banking divisions.
Barclays chief executive Antony Jenkins is leading an overhaul to improve results and repair its tarnished image following the group's £290 million fine for rigging the Libor rate.
He is expected to set out new financial targets when he presents the bank's results on February 11.
Last year Mr Jenkins announced that at least 3,700 jobs would be cut to reduce costs by £1.7 billion, and revealed in shareholder meetings last March that the bank was considering using technology and automation to drastically reduce its workforce further.
Yesterday it was reported that Barclays has ordered staff to cut out all non-essential overseas travel.
The group has banned employee travel for internal meetings and restricted wider international travel for only essential client and regulator discussions, according to Sky News.