A third of the City watchdog's staff plans to leave in the next two years, according to a confidential staff survey that comes as the regulator faces a heavy toll from the external and internal strains of the last year.

Responding to an internal questionnaire, 34 per cent of the 2,740 staff at the Financial Services Authority said they planned to leave. The numbers were revealed in a letter from chief executive Hector Sants to Adam Price, Plaid Cymru MP, in response to parliamentary questions.