The Royal Bank of Scotland Group has announced it is closing 259 of its branches, including 62 Royal Bank of Scotland and 197 NatWest branches.
This is the equivalent to a quarter of the existing branch network, which RBS said would result in about 680 job losses.
RBS said it made the closer because more customers are turning to online banking rather than visiting branches.
An RBS spokesperson 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% and mobile transactions have increased by 73% over the same period. Over 5 million customers now use our mobile banking app and one in five only bank with us digitally.
“We realise this is difficult news for our colleagues and we are doing everything we can to support those affected.”
However Unite the Union said 1,000 employees face losing their jobs.
Rob MacGregor, Unite’s 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.
“This announcement will forever change the face of banking in this country resulting in over a thousand staff losing their jobs and hundreds of high streets without any banking facilities.”
RBS, which is 71% owned by the taxpayer, is expected to announce, in its report in February, it will have incurred 10 years of full-year losses since their taxpayer bailout in 2008.
This week Lloyds Banking Group said it will close 49 branches, including 32 under the Lloyds brand, 11 Bank of Scotland outlets and six Halifax branches.