The Financial Services Authority (FSA) has charged four men with conspiracy to commit insider dealing in what the agency claims is its largest and most complex insider trading investigation to date.

Martyn Dodgson, a former senior corporate broker at Deutsche Bank; Andrew Hind, a director of Deskspace Offices; private stock broker Benjamin Anderson; and businessman and investor Iraj Parvizi have been bailed to attend Westminster Magistrates' Court on 19 October. The allegations relate to activities between 2006 and 2010.

Dodgson is being represented by Giles Bark-Jones of Bark & Co, with Michael Potts of Byrne and Partners advising Anderson. Peter Hughmans of Hughmans Solicitors is acting for Parvizi, and Lewis Nedas' Miles Herman is representing Hind.

All four men were arrested in a series of raids at 16 addresses in London, the southeast and Oxfordshire in March 2010 as part of Operation Tabernula, a long-running joint investigation by the FSA and the Serious Organised Crime Agency.

At the time the FSA alleged that the City professionals had made significant profits by passing inside information to traders (either directly or via middlemen), who traded based on this information as part of a £3m conspiracy.

The FSA confirmed a number of individuals remain under investigation. At the time of the searches in 2010, three others were arrested, and since then a further two individuals have been arrested and taken in for questioning.

The prosecutions are the latest evidence of the tougher enforcement stance since the watchdog came in for intense criticism for failing to police major banks in the run-up to the 2008 banking crisis. The harder line from regulators has already led to a boom in white collar defence and investigations work for corporate law firms.

Fourteen convictions in relation to insider trading have so far been secured by the FSA, including the jailing last year of Dresdner investment banker Christian Littlewood. Four other individuals are also awaiting separate trials.

Commenting on the FSA's strategy, Stephenson Harwood litigation partner Tony Woodcock said: "It appears the FSA is now reaching those individuals whom they said it would take time to reach because of the complexity of the investigations. To begin with, and so that people would take them seriously, the FSA prosecuted the smaller cases: one or two individuals."

He added: "They always said more time would be needed to grapple with the serious players in cases where the misconduct is well-hidden by sophisticated individuals using sophisticated means. They are now beginning to do so. This is very much a natural progression."

The FSA in August appointed Tracey McDermott as its new director of enforcement and financial crime, replacing Margaret Cole, the former litigator who quit the body in March to head the legal team at PricewaterhouseCoopers. The appointment comes amid a period of upheaval for the FSA, which is being reformed as the new Financial Conduct Authority as part of a Government shake-up of market regulation.

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