Barclays suspended six currency traders last week as it comes under investigation for possible manipulation of foreign exchange trading.
The bank, which is still looking to repair its reputation following its role in the Libor interest rate-rigging scandal, said it was unable to predict the fallout of the latest worldwide probe into financial sector activity.
Last year, Barclays, along with other international banks, was fined for manipulation of the Libor inter-bank lending rate.
Regulators around the world are now investigating the currencies market and Barclays, RBS, Citigroup, Deutsche Bank and UBS have all confirmed that regulators have been in contact with them over the currency probe, though there is currently no evidence of wrongdoing, the BBC reports.
Under particular scrutiny is instant messaging and whether that was used by traders to help co-ordinate the fixing of official currency rates to their advantage so they could make a profit.
The global foreign exchange market is worth more than $US5 trillion a day, and London is the most important hub, accounting for about 40% of all foreign-exchange trading.