The Serious Fraud Office (SFO) has dropped its case into forex rigging, concluding there is insufficient evidence to convict.
The regulator said “while there were reasonable grounds to suspect the commission of offences” it has closed the investigation.
In a statement, the SFO said the evidence, “would not meet the evidential test required to mount a prosecution for an offence contrary to English law.”
It concluded that: “evidential position could not be remedied by continuing the investigation.”
The SFO worked with the Financial Conduct Authority (FCA) on the investigation, which was launched in July 2014.
It was alleged that a number of traders were using chat rooms to manipulate benchmark pricing in the foreign exchange market.
Martin Wheatley, head of the FCA at the time the investigation began, said the case was “every bit as bad” as the Libor scandal.
Earlier this month two former traders for Rabobank were handed prison sentences in relation to Libor rigging.
The SFO’s investigation into forex rigging involved over half a million documents, and lasted over one and half years.
The UK’s Financial Conduct Authority has already made a series of fines in relation to market abuse.
In April 2015, it fined Deutsche Bank £227 million, in July 2014, it fined Lloyds Banking Group £105m and in June 2012, it fined Barclays £59.5m.
The FCA’s predecessor, the Financial Services Authority, fined UBS £160m in relation to Libor and Euribor manipulation at the end of 2012.