The SFO's probe into alleged manipulation of benchmark rates such as Libor (London interbank offered rate), which began in 2012, has so far resulted in five convictions and six acquittals of individuals. Eight others face trial next year.

SFO director David Green told a parliamentary committee of lawmakers that there were also "some others" who it had to decide whether to charge.

Lawmakers asked whether the SFO had the resources to provide a credible threat of prosecution if companies failed to report themselves to the authorities when they discover wrongdoing.

Green said he had spent four years speaking at least fortnightly with businesses and lawyers explaining the incentives behind self-reporting, while building up the agency's intelligence division.

"You will see over the coming months some significant deferred prosecution agreements (DPAs)," he said.

DPAs, effective plea deals introduced in Britain in 2014, were a useful tool to encourage good corporate conduct, Green said, and were available to those who report wrongdoing promptly, cooperate, grant authorities access to factual documents and assist in prosecuting individuals.

A judge approved Britain's first DPA in November in a case centred on $6 million in bribes paid to Tanzanian officials by the Tanzanian unit of South Africa's Standard Bank (>> Standard Bank Group Ltd).

Tesco (>> Tesco PLC) is among companies cooperating with a criminal inquiry into accounting practices, launched after the supermarket chain said it overstated half year profits in August 2014 by about 260 million pounds ($320 million).

Green also said a new line of inquiry had also been opened in a three-year inquiry into global outsourcing group Serco (>> Serco Group plc), launched after an audit alleged the government had been charged for tagging criminals who were either dead or in prison.

The SFO head gave no further details on the Libor inquiry, a global investigation in which it has charged around 20.

Barclays (>> Barclays PLC), which has seen 10 former traders charged for alleged benchmark rigging and admitted in 2012 to low-balling, or artificially lowering, rates during the credit crisis, reiterated in its 2015 annual report that it continued to respond to information requests as part of an SFO inquiry.

(Editing by Alexander Smith)

By Kirstin Ridley