(Reuters) - Britain's biggest banks face another 19 billion pounds of charges relating to past misconduct over the next two years, ratings agency Standard & Poor's (S&P) said in a report on Monday.

S&P said Britain's banks and customer-owned lenders had incurred 48 billion pounds in misconduct and litigation charges over the past five years.

Britain's four biggest banks -- Barclays, HSBC , Lloyds Banking Group and Royal Bank of Scotland -- accounted for 42 billion of that total, equivalent to about 7.5 percent of their revenues, S&P said.

S&P said the mis-selling of payment protection insurance (PPI) on loans and mortgages had so far cost the banks more than 26 billion pounds. It expects banks to face over 5 billion pounds of further PPI charges in the next two years.

Banks also face litigation charges arising from investigations into the alleged rigging of foreign exchange markets and benchmark interest rates and probes into breaches of anti-money laundering controls.

S&P said it believed the affected banks had sufficient capital buffers to cope with the charges.

The charges came on top of almost 16 billion pounds spent by the banks restructuring their business models following the 2007-9 financial crisis and 5 billion pounds of expenses relating to the government's bank levy, S&P said.