The potential layoffs will occur in the bank's fraud operations, central operations and across TSB's branch network, Unite said, adding that it would seek talks with management in an effort to reduce any additional redundancies.
The proposed layoffs come just three months after TSB announced plans on February 6 to cut around 300 positions in its Risk and Finance, Customer Banking and Customer Delivery teams.
"To meet the changing needs of customers and for TSB to remain competitive, we are making changes to simplify the way we operate," the bank's spokesman said in a statement Wednesday.
"These decisions are never taken lightly. Our priority is to consult with affected colleagues to ensure they receive our full support, maximizing outplacement opportunities where we can."
Unite regional head Andy Case called the bank's plans a "serious mistake."
"These workers do essential work in fraud departments and across the branch network. TSB customers will rightly be concerned by today's news and will undoubtedly suffer a drop in service as a result of these job cuts."
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(Reporting by Sinead Cruise; editing by Amanda Cooper; Spanish editing by Javi West Larrañaga)
