Fresh from the Libor scandal, a global investigation into alleged currency market manipulation has been expanded to include 15 of the world's biggest banks.
Authorities allege currency traders may have shared information amongst themselves before they shared it with their clients.
It follows the Libor investigation where several global banks were found to have illegally fixed interest rates, which affect a vast arrange of financial products including mortgages.
The currency investigation is being conducted by 7 different country regulators, led by the UK.
The BBC reports that public distrust of banks is rising, because people are speculating that the original manipulation of Libor rates may not have been a one-off, incident, but part of a pattern of behaviour in other trading.
The probe now includes euro-dollar trading, the biggest part of the market.
Last month Britain's Financial Conduct Authority (FCA) said it was examining whether traders had colluded.
Regulators in Switzerland, Hong Kong and the US are also involved.
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.
Several banks have confirmed that they are co-operating with the investigation, including Royal Bank of Scotland, JP Morgan Chase, Citigroup and Barclays.
Earlier this month Barclays suspended six traders as part of a probe into suggestions that currency markets could have been rigged.
Suspicions of exchange rate manipulation centre on a one-minute window of trading at 16:00 every day that is used to set exchange rates.
The suggestion is that traders colluded to push through high volumes of trades in the run-up to and during the window to influence rates.
Last month Royal Bank of Scotland (RBS) suspended two traders in connection with the investigation into the currency markets.
