In a letter sent by FSA chairman Adair Turner to Barclays chairman Marcus Agius on April 10th 2012, the FSA accused the bank of being too 'aggressive'.
"The purpose of my meeting with you was therefore not to focus on any one specific issue which requires remedial action. Rather I wished to bring to your attention our concerns about the cumulative impression created by a pattern of behaviour over the last few years.
"In which Barclays often seems to be seeking to gain advantage through the use of complex structures, or through arguing for regulatory approaches which are at the aggressive end of interpretation of the relevant rules and regulations."
Bob Diamond tonight angrily rejected suggestions that he misled MPs over regulators' concerns about activities at Barclays.
The Bank of England's Paul Tucker told MPs he refuted claims that he attempted to influence Barclays into manipulating the Libor rate.
MPs will be hoping the Deputy Governor of the Bank of England will shed some light on unanswered questions about rate-fixing at Barclays.