A spokeswoman for RBS said "the world had changed since then", and there had been a 30% fall in branch transactions over the last four years.
In its customer charter of 2010, RBS said it would not close any bank which was the last one in the community.
It promised "to stay open for business if we are the last bank in town, and consider a range of options to ensure a local banking service is available".
A spokesman for RBS said:
"Banking has changed significantly over the last few years as more and more of our customers are banking with us where and when it is convenient for them.
"We have to adapt to what our customers want, which is why we're investing in a range of other ways our customers can bank with us, including online and telephone banking, our mobile app, and in any one of the Post Office's 11,500 branches across the UK."
Peter Savage, MD, Azule Finance, said:
“Banks are being forced to drive efficiencies to the point where wholesale branch closures are taking place. These cut-backs are far from over – will the traditional bank model even exist five years from now?
“This move should sound a warning to individuals and businesses that the traditional big banks are in a state of flux. RBS has no problem with letting down vulnerable customers who rely on them as the last bank in town, and it would not be surprising to see them disappoint businesses in a similar way.
“Businesses that regularly use overdrafts, borrow and lease assets would be wise to seek alternative means of financing these activities.”
