Barclays and Royal Bank of Scotland are set to plead guilty this week to charges of rigging the foreign exchange market, with fines running into almost £3bn.
The two banks are among the institutions that have been under investigation of manipulation of currency benchmarks since 2013. The Sunday Times reports both are set to accept substantial fines levied by UK and US regulators.
Barclays previously opted out of a joint settlement on currency manipulation in November which saw six banks including RBS and HSBC paying a £2.7bn collective fine.
In making a deal with authorities this week, the British banks are expected to pay up to a further £3bn in settlements.
US banking giants JP Morgan and Citigroup will also plead guilty to the rigging charges and are expected to pay billions of dollars in fines.
Guilty pleas would come as the FCA continues to punish City institutions in the aftermath of the Libor manipulation scandal.
Only last month, the FCA slapped Deutsche Bank with a record £1.3bn fine over Libor.