Britain's Financial Services Authority said on Monday that four men have been charged with insider dealing following the watchdog's most complex investigation of its kind so far.
Martyn Dodgson, a senior corporate broker, Andrew Hind, Benjamin Anderson and Iraj Parvizi have been bailed to attend Westminster Magistrates Court on 19 October 2012.
A number of individuals remain under investigation, the FSA said in a statement.
The charges stem from Operation Tabernula, a joint probe by the FSA and the Serious Organized Crime Agency who raided 16 addressed in London, the south east and Oxforshire in March, seizing documents and computers.
At the time, six men were arrested, including two senior city professionals at leading institutions and one professional at a hedge fund.
(Reporting by Huw Jones, editing by Laurence Fletcher)