TSB will close 164 of its branches and cut 960 jobs, blaming “a significant shift in customer behaviour” as more customers bank online.
The figure is in addition to the 82 branches it said it would close in November, when it set out plans to save £100m by 2022.
Union Unite described the move as “a dark day for the finance sector”.
The bank said the closures were not an “easy decision” and had been accelerated by the pandemic.
From the end of next year the bank will have 290 branches – down from 540 currently.
It hopes most of the job cuts will come through voluntary redundancies, and said it would also create 120 new positions.
TSB did not name which branches would shut, but said those with the lowest footfall would go.
“Our customers are banking differently – with a marked shift to digital banking,” said boss Debbie Crosbie.
“This means having the right balance between branches on the high street and our digital platforms, enabling us to offer the very best experience for our personal and business customers across the UK.”
The bank said it was seeing 1,200 new registrations for online and mobile banking every day back in November – but that had risen to more than 4,000 during the pandemic.
Unite’s national officer Dominic Hook said: “Unite has argued for some time that the financial services industry has a social responsibility not to walk away from its local customers who continue to need access to banking in bank branches.
“It beggars belief that just seven years ago TSB had 631 local branches and this announcement will reduce that number to merely 290 branches. “
TSB is the latest bank to announce closures during the pandemic.
In August the Co-operative Bank has said it will cut 350 jobs and close 18 branches due to the current “economic uncertainty” and the shift to online banking.
Natwest Group also said it would cut 550 jobs in branches and close one of its remaining offices in London.
TSB, which is owned by Spanish lender Banco Sabadell, has been dogged by technical problems, with an IT failure last year leaving up to 1.9 million customers unable to bank online for several weeks.
Customers were moved on to a new system, but an investigation found it had not been tested properly before going live. It cost TSB a total of £330m for customer compensation, fraud losses and other expenses.
As recently as last month users unable to access online banking. And last year, a “processing error” meant wages and other payments were not paid into some TSB customers’ accounts.