Royal Bank of Scotland (RBS) has been fined £56mln ($87mln) by regulators after a 2012 software issue left millions of customers unable to access accounts. RBS, NatWest, and Ulster Bank customers were affected in June 2012 after problems with a software upgrade, BBC News reports.

The Financial Conduct Authority fined RBS £42mln, and the Prudential Regulation Authority fined the bank £14mln.

RBS chairman Sir Philip Hampton said the problems "revealed unacceptable weaknesses in our systems".

In 2012, the bank set aside £125mln in compensation and costs because of the disruption.

The fine comes on top of a £217mln FCA penalty for RBS last week over foreign exchange rate rigging.