RBS is to close 32 NatWest branches with the loss of up to 600 roles.
Unite the union says the banking group is shutting offices in the North, Midlands, East and London, with closures to affect other regions in coming weeks.
The North will see 18 branches close, up to 217 roles lost and 220 branches change their opening hours.
RBS will close 13 branches in the Midlands and East, with as many as 176 roles lost and 94 branches tweaking their trading hours.
London and the South East will see one branch close, and more than 200 role losses.
It is not yet clear which type of roles will be cut.
Unite regional officer Lyn Turner says: “With job losses across the country and surviving branches on reduced hours, there’s no doubt this latest round of cuts will hurt the bank’s customers as well as our members.
“With every branch closure NatWest is slamming its doors on another community, dangerously undermining the bank’s long-term future.
”Unite will consult with our members as we hold the bank to its promise to avoid compulsory redundancies.”
Unite the union is in negotiations with RBS over the proposed March job cuts.
RBS could not be reached for comment.