Moody's has threatened to downgrade Barclays' credit rating because of the impact on the management structure of the Libor scandal.
The ratings agency warned over the difficulty of replacing key senior staff including the former chief executive Bob Diamond.
The agency also said it was concerned about the cultural changes needed at Barclays, an issue highlighted when Diamond was grilled by MPs yesterday.
Diamond quit on Tuesday along with close colleague Jerry del Missier who was promoted to chief operating officer only last month, while chairman Marcus Agius will also go once he has replaced the chief executive following the £290m fine for manipulating Libor (the London Interbank Offered Rate).
Meanwhile agency S&P also warned that = "weak compliance" and "current management flux" had knocked the company's outlook.