Three former Barclays traders appeared in a London court on Wednesday charged with running a two-year scheme to manipulate Libor benchmark interest rates.

The men, who spoke only to confirm personal details such as addresses, bring to six the number facing criminal charges in Britain over allegations that they rigged the London Interbank Offered Rate, against which about $450 trillion of financial products are pegged, from student loans to complex derivatives.

The sprawling Libor investigation, which stretches from North America to Asia and has shaken faith in the financial industry, has so far resulted in 10 banks and brokerages being fined a total of $6 billion and charges brought against 13 individuals.

Britain's Serious Fraud Office (SFO), keen to silence critics who have questioned its ability to secure convictions for complex financial crimes, alleges that the latest trio either submitted or agreed to procure false or misleading dollar Libor rates to boost the trading positions of Barclays staff.

Peter Charles Johnson, 59, Jonathan Mathew, 33, and Stylianos Contogoulas, 42, all face one count of conspiracy to defraud between June 2005 and August 2007.

The three men, whose case has been sent to the higher Southwark Crown Court for Feb. 3, did not indicate any plea and have been granted conditional bail.

The SFO has already charged three men as part of its Libor investigation, including Tom Hayes, a former yen derivatives trader at UBS and Citigroup, who pleaded not guilty in December.

Hayes is due to stand trial in January 2015 on eight charges of conspiring with staff from at least 10 major banks and brokerages to manipulate yen Libor rates between 2006 and 2010.

Terry Farr and James Gilmour, two brokers from RP Martin, have been charged and pleaded not guilty to similar fraud-related offences. Their trial has been scheduled for September 2015, in part to allow the SFO time to bring charges against further alleged co-conspirators.