US regulators have forced Citigroup to hire external consultants to consider whether its current management is up to the job of leading the troubled bank out of the financial crisis, in a decision that intensifies pressure on its top executives and board.

People close to the situation said Citi had retained Egon Zehnder, a headhunter and board advisory consultancy, to carry out an in-depth management review requested by the government after stress tests on banks in May.