Britain's fraud agency has charged three former Barclays bank employees for their alleged manipulation of the Libor interest rates.

The Serious Fraud Office (SFO) said on Monday that it has charged Peter Charles Johnson, Jonathan James Mathew and Stylianos Contogoulas with conspiracy to defraud between June 2005 and August 2007.

The bank declined to comment.

Libor, or the London Interbank Offered Rate, is the rate at which a bank can borrow from its treasury and lend to a client. 

It is alleged that traders agreed to rig rates during the financial crash of 2008 to hide the financial stress their banks were under, and also to make more money in their trades.

The manipulation had knock-on effects for many financial and commercial markets, indirectly causing rates on mortgages and loans to fluctuate.

At least six people have been implicated in the manipulation of the rate.

The SFO last year brought charges against three former employees of Swiss bank UBS and UK brokerage RP Martin, the first people to face trial in connection with a global investigation into a rate-rigging scandal that sparked intense criticism of standards across the industry.

Barclays paid $450mn in July 2012 to settle allegations from the US and UK regulators that it had manipulated Libor to keep it low. Its chairman and chief executive later resigned following a barrage of criticism about its standards and culture.

The SFO's investigation into Libor began in July 2012 and it said it continues to work with Britain's Financial Conduct Authority and the US Department of Justice on the case.

It said the former Barclays staff would appear at Westminster Magistrates' Court at a future date.

UBS, Royal Bank of Scotland and Rabobank have been fined a total of $3.6bn by US and British regulators for alleged Libor manipulation. More banks are expected to face fines as regulators continue to investigate.

The SFO is under pressure after a series of high-profile setbacks, and its boss David Green has staked his reputation on the success of high-profile investigations such as Libor.

It brought charges in relation to alleged Libor rigging against Tom Hayes, a former trader at UBS and Citigroup, last June and started proceedings against Terry Farr and James Gilmour, former brokers at RP Martin, last July.

The three men pleaded not guilty in December. Hayes' trial is expected to start in January 2015.

Source: Agencies