The penalty specifically relates to market abuse regulations introduced in 2016 to monitor the threat of insider trading or market manipulation.

These rules mandated that firms monitored all trading activity across a wide range of markets and instruments.

According to an FCA statement, Citigroup Global Markets, the investment bank’s UK-based international broker dealer arm, failed to apply these rules up until January 2018, resulting in "significant gaps in its arrangements, systems, and procedures for additional trade surveillance".

During the 18 month period in quesitons, Citi earned more than £2.5bn for arranging and executring trades.

The firm also managed to reduce the fine from £18m by applying for a 30% discount in exchnage for agreeing to resolve the case.

"The framework for market integrity depends on the partnership between the FCA and market participants using data to detect suspicious trading," said Mark Steward, executive director of enforcement and market oversight at the FCA.

"By not fully implementing the new provisions when required, Citigroup Global Markets did not carry its full weight in this partnership, impacting market integrity and the overall detection of market abuse."

In a statement, Citi said it was "please to put the matter behind us".

The Financial Times also reported that the bank’s chief executive Jane Fraser has put aside $11bn for its technology budget this year in order to get a grip on its regulatory reorting requirements