Sir Hector Sants is to take a leave of absence from his role at Barclays as a result of a diagnosis of exhaustion and stress, according to Barclays spokesman.
The former regulator is not expected to return to work until 2014.
Sants started work at Barclays in January of this year, reporting directly to chief executive Antony Jenkins. He resigned his role as head of the Financial Services Authority in June 2012.
Hector Sants begins his City career at stockbroker Phillips and Drew, from where he moved to hold positions as vice chairman of UBS and chairman of Donaldson, Lufkin & Jenrette.
Sants joins Credit Suisse First Boston as a member of its executive board and chief executive of the Europe, Middle East and Africa region.
Sants is recruited by the Financial Services Authority as managing director for wholesale and institutional markets, responsible for all regulated markets and the operation of the UK listing rules.
Sants appointed to succeed John Tiner as chief executive of the regulator, just before the UK economy was sent into a tailspin by the downfall of Northern Rock.
FSA publishes an internal review of its dealings with Northern Rock, revealing a catalogue of errors in its supervision of the bank. Sants admits that those responsible for monitoring the Rock had failed to come up to scratch in their “engagement and oversight” of the bank.
FSA comes under fire after its annual report accounts reveal directors were paid a total of £3.2m in the 2007-8 year, up 22 per cent on the previous year despite its botched handling of the Northern Rock affair.
Sants claims that the City “should be very frightened of the FSA”, after initiating a wide-ranging overhaul of the regulator’s practices in order to crack down on risky banking practices.
Sants throws support behind the City’s existing regulatory system of “integrated supervision” at the FSA’s annual public meeting, putting him on a collision course with the Tories, who plan to hand back the supervision of bank risk to the Bank of England if they win the next election.