The Serious Fraud Office confirmed it has gathered extensive evidence against of the former UBS and Citi trader Tom Hayes for his role in the manipulation key interbank lending rates.
According to prosecutors in a preliminary court hearing Westminster Magistrates Court on Thursday, the SFO said it has enough evidence to prosecute Hayes over Libor rigging charges.
Judge Anthony Leonard told SFO lawyers that they have until 30 September to serve prosecution papers.
"To describe [the evidence] as voluminous would be rather an understatement," said the leading counsel Mukul Chawla in the hearing.
Hayes attended the hearing to only confirm his name. He also did not enter a plea agreement.
On 18 June, the SFO charged Hayes with eight counts of fraud, in connection with the investigation by criminal investigation unit into the manipulation of Libor.
The SFO confirmed he was one of the three individuals arrested and interviewed on 11 December, 2012.
A day after being questioned by UK authorities, the US Justice Department charged Hayes with fraud, conspiracy and an antitrust violation and he faced possible extradition proceedings.
It also charged former UBS trader Roger Darin with conspiracy. Since the SFO has charged Hayes with criminal offences, it would allow the UK to stake a jurisdictional claim to the British suspect.
Barclays was the first to settle with US and UK authorities in June last year over its role in the Libor fixing scandal.
In December, UBS agreed a record $1.5bn fine with US, UK and Swiss authorities for its role in manipulating a number of key benchmark interbank lending rates.
The UBS Japanese unit, where Hayes had previously worked, also pleaded guilty to US criminal charges by admitting to one count of wire fraud relating to rigging rates in Yen.
Hayes joined UBS in Tokyo in 2006 when he was 27 and later became a senior and highly valued trader of interest rate derivatives indexed to yen-denominated Libor. His trading generated nearly $260m in revenues by late 2009, say reports, but he left UBS to join Citigroup after a dispute over his salary package.
However, Citi fired him less than a year later after colleagues allegedly raised concerns about inappropriate Libor requests.
A RBS subsidiary, RBS Securities Japan Limited, also pleaded guilty to one criminal charge of wire fraud.