Britain's Serious Fraud Office is charging three former Barclays employees in a scandal related to the rigging of a key market interest rate.

Authorities say criminal proceedings have begun against Peter Charles Johnson, Jonathan James Mathew and Stylianos Contogoulas for actions between June 1, 2005 and Aug. 31, 2007.

A court date has not yet been set to enter pleas.

At least six people have been implicated in the manipulation of the London interbank lending rate, known as LIBOR. The rate is used by banks to borrow from each other and indirectly affects the cost of loans in the wider economy.

If convicted, the traders could face up to 30 years in prison.

Britain's Barclays and Royal Bank of Scotland, Switzerland's UBS and the Dutch Rabobank have been fined a total of $3.6 billion by U.S. and British regulators for manipulating LIBOR.

Barclays and its subsidiaries paid about $453 million US to regulators to settle charges related to rate-fixing between 2005 and 2009.

Barclays chief executive Bob Diamond and chairman Marcus Agius resigned in 2012 after the scandal.

Last month, three former Rabobank traders were charged in the US over allegedly conspiring to manipulate the Yen Libor benchmark interest rate since 2006.

The banks have been stripped of authority to set the Libor rate, which is now managed by NYSE Euronext.