TOM Hayes, the former UBS AG and Citigroup Inc trader, conspired with employees of at least five other banks and three interdealer brokers over a four-year period to manipulate yen Libor rates, prosecutors said.

Hayes appeared at a London criminal court for the first time yesterday where prosecutors laid out the charges against him. The 33-year-old was charged with working with employees at JPMorgan Chase & Co, Royal Bank of Scotland Group Plc, HSBC Holdings Plc, Rabobank Groep and Deutsche Bank AG, as well as Tullett Prebon Plc, ICAP Plc and RP Martin Holdings Ltd, the UK Serious Fraud Office said in documents read out yesterday.

The charges come almost a year after Barclays Plc became the first of three banks fined as part of global regulators' probes into the London interbank offered rate and other benchmarks. Hayes has also been charged by the US Justice Department, which is running a parallel criminal investigation.

Hayes tried to manipulate rates "with the intention that the economic interests of others would be prejudiced and/or to make personal gain for themselves or another," UK prosecutors said in the indictment.

Hayes faces eight counts of conspiracy to defraud in the case, four covering the period from August 8, 2006, until December 3, 2009, while he worked at UBS, and the other four from December 1, 2009 until September 7, 2010, when he was at Citigroup.

Charges haven't been filed in the UK against anyone else in the investigation related to the manipulation of Libor.