Credit Suisse’s back office raised questions internally in the five months before the Swiss bank announced $2.7bn (£1.4bn) of mispriced trades in February, but a deferential attitude to the trading desk prevented it following through on the concerns.

The finding was made by the Financial Services Authority on Wednesday as it fined Credit Suisse £5.6m for systems and controls failures implicated in the trading scandal. The regulator did not conduct its own investigation, relying instead on the probe conducted by Credit Suisse.