The City regulator has charged a fifth person for insider dealing in a case involving alleged front-running, when a trader takes a position to capitalise on advance knowledge.
Richard Baldwin, 46, was charged by the Financial Services Authority earlier this week following an investigation codenamed Operation Tabernula.
The FSA arrested seven people and raided 16 addresses in London and the South-east in 2010 as part of the crackdown.
At the time of the first arrests, the FSA said it believed "City professionals passed inside information to traders – either directly or via middlemen – who traded on this information and have made significant profits".
Mr Baldwin's lawyer told Bloomberg that he denied the allegations made against him. He faces three charges relating to insider dealing and acquiring money "being the proceeds of crime".
Operation Tabernula is the "largest and most complex insider dealing investigation to date", the FSA has said.
Martyn Dodgson, a former Deutsche Bank managing director, is among those charged in the investigation, which has spanned two and a half years.
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