Royal Bank of Scotland is closing a quarter of its UK branch network, with 680 redundancies.
The announcement will affect 62 RBS branches and 197 NatWest branches - a total of 259, leaving the company with 744 across the UK.
An RBS spokesman said: "More and more of our customers are choosing to do their everyday banking online or on mobile.
"Since 2014 the number of customers using our branches across the UK has fallen by 40 per cent and mobile transactions have increased by 73 per cent over the same period. Over five million customers now use our mobile banking app and one in five only bank with us digitally."
The bank acknowledged the redundancies would be "difficult news" for its staff and said it would try to keep compulsory redundancies to a minimum and support those affected.
Earlier this year RBS, which is still majority-owned by the government, announced it would be shutting 158 branches because of a "dramatic shift" in banking towards digital.
RBS said it would be writing to the customers affected to let them know about alternative ways of banking with the company.
Rob MacGregor, Unite national officer, said: “The Royal Bank of Scotland has decided to decimate its bank branch network. Now serious questions need to be asked about whether these closures mark the end of branch network banking.
"The closure of another 259 branches is savage and represents a betrayal of loyal staff and customers who have supported the bank for decades. Why is the government signing off this alarming branch closure program?
"A decade of slashing jobs has done nothing to boost morale, increase consumer confidence or improve the bank’s performance. This British-taxpayer funded bank should be concentrating on investing in jobs here in the UK, rather than cutting them wholesale."
Earlier this week Lloyds Banking Group announced the closure of 49 branches, saying its customers are increasingly choosing to use digital and mobile channels.