Royal Bank of Scotland has announced that it is to close 162 branches across England and Wales.
"Customers of Royal Bank of Scotland in England & Wales will be able to use NatWest branches instead for their everyday banking needs."
The latest branch closures follow existing plans to close 52 bank branches in Scotland that serve rural communities.
The Unite union has calculated that in the case of 71 of the 162 branches closing, customers will be forced to make return journeys of about 25 miles to reach another one.
Rob MacGregor, Unite's national officer, said: "The Williams & Glyn saga rolls on as Royal Bank of Scotland continues with its shambolically poor management of this business.
"How does a taxpayer-funded institution spend £1.8bn on a failed IT project and in the next breath demolish the much-needed local bank branches?
"Today nearly 1,000 employees have finally been told of their dark futures because the bank has been calamitously managed for too long.
"Ending years of speculation, Royal Bank of Scotland has effectively turned its back on the Williams & Glyn customers and staff."
In February, following a campaign by local communities, RBS decided to keep 10 branches threatened with closure open till the end of the year.
Unite is calling on RBS "not to abandon their responsibilities" to the communities that depend on the affected bank branches.
"These plans can not be put into motion, for the sake of consumers and staff," the union said.
"The reality is that as a result of these planned closures, the overwhelming majority of customers will find themselves without access to full banking facilities and in the most extreme examples, some will find themselves having to make a round trip of circa 130 miles."