The move was hailed by the FSA earlier this year as a "new world of judgement-based regulation."
The change comes ahead of the move to the Prudential Regulation Authority (PRA) and Financial Conduct Authority (FCA) in 2013.
The FSA hopes by implementing a twin peaks model early, it will cause minimum disruption when the PRA and FCA are formed.
Since the change was announced, two senior members have announced their departure from the organisation.
Chief executive Hector Sants, who was key to the changes to the regulatory model, has handed in his resignation and is due to leave at the end of June.

As well as his role in setting up the new model, he was appointed chief executive designate of the PRA and was a member of the Financial Policy Committee, the third committee in the new tri-partite system, at the Bank of England.
His colleague Margaret Cole, head of the conduct business unit and former head of enforcement, also announced in February that she would be leaving the regulator in April.
She has since announced that she will be moving to a legal role at financial services firm PricewaterhouseCoopers.