The FSA is thought to be determined to appoint someone with extensive banking experience after its self-confessed failure in its handling of Northern Rock.
An external candidate has been deemed by the City to be essential after the recent internal appointment of Hector Sants as chief executive.
A source says: “The list has been narrowed down to the final six and there seems to be an emphasis to get somebody from the banking sector, an existing executive, for example, given everything that has happened. I think that it will be at least another six to eight weeks before a name will come out.”
McCarthy, who was previously chairman and chief executive of Ofgem, is set to step down in September after five years at the FSA.
The recruitment procedure is carried out by the Treasury. Both the Treasury and the FSA declined to comment.