Osborne to announce new rules on foreign currency markets
11 June 2014 Last updated at 23:15 BST
The manipulation of foreign currency markets by bankers is to be made a criminal offence.
BBC News understands that the Chancellor George Osborne will use his speech at Mansion House tomorrow to unveil new rules, following allegations that the multi-trillion-pound market was being fixed.
The market is largely unregulated and a number of major banks are facing inquiries.
The BBC's business editor Kamal Ahmed reports.