Switzerland's competition commission WEKO said today it had opened an investigation into several Swiss, British and American banks over potential collusion to manipulate foreign exchange rates. 

WEKO said it is investigating UBS, Credit Suisse, Zuercher Kantonal Bank, Julius Baer, JP Morgan, Citigroup, Barclays and Royal Bank of Scotland.

"Evidence exists that these banks colluded to manipulate exchange rates in foreign currency trades," WEKO said in a statement.

Given its current information, WEKO said it assumed that the most important exchange rates are affected.

The competition authority opened a preliminary investigation last October after learning about potential manipulation of foreign exchange markets by banks.

Authorities in the US, UK, Germany and Singapore are also looking into allegations of collusion and manipulation of the global foreign exchange market.

They are examining not only whether traders from different banks worked together to influence currency prices, but also whether they traded ahead of their own customers or failed to accurately represent to customers how they were determining the prices.