The banks are Bank of America, JP Morgan, Citigroup, Wells Fargo, Goldman Sachs and Morgan Stanley. The costs cover legal bills, funding in-house legal teams, litigation and claims payments, according to Bloomberg Businessweek which compiled the data. Well over a third (40 per cent) of the expenses have been run up since January 2012 - with banks warning that the costs could surge under pressure from regulators, prosecutors and investors.

'There may be a sense that financial institutions have gotten away with a lot and maybe now is the time to catch up,' lawyer Daniel Hurson, former a prosecutor at the Securities and Exchange Commission, told Businessweek.