The regulator added that submissions on Libor and Euribor took into account requests from interest rate derivatives traders, who were motivated by profit and sought to benefit from Barclays' trading positions.
The breaches involved a significant number of employees and occurred over a number of years, the FSA added.
Mr Diamond said: "I am sorry that some people acted in a manner not consistent with our culture and values.
"The events which gave rise to today's resolutions relate to past actions which fell well short of the standards to which Barclays aspires in the conduct of its business.
"Nothing is more important to me than having a strong culture at Barclays."