The banks and their fines are: Citibank N.A. £225,575,000 ($358 million), HSBC Bank Plc £216,363,000 ($343 million), JPMorgan Chase Bank N.A. £222,166,000 ($352 million), The Royal Bank of Scotland Plc £217,000,000 ($344 million) and UBS AG £233,814,000 ($371 million) ('the Banks').
The FCA says that the G10 spot FX market is a systemically important financial market and in addition to the fines it will also launch "remediation" to investigate and correct faults in the market.
The FCA said: "At the heart of today's action is our finding that the failings at these banks undermine confidence in the UK financial system and put its integrity at risk.
"In relation to Barclays Bank Plc, we will progress our investigation into that firm which will cover its G10 spot FX trading business and also wider FX business areas.
"In addition to taking enforcement action against and investigating the six firms where we found the worst misconduct, we are launching an industry-wide remediation programme to ensure firms address the root causes of these failings and drive up standards across the market. We will require senior management at firms to take responsibility for delivering the necessary changes and attest that this work has been completed."
The regulators says that the fines complement its ongoing supervisory work and wider reforms to the fixed income, commodity and currency markets which are the subject of the UK Fair and Effective Markets Review.
The fines relate to poor controls at the banks between 1 January 2008 and 15 October 2013. The watchdog says that these "ineffective" controls allowed G10 spot FX traders to put their banks' interests ahead of those of their clients, other market participants and the wider UK financial system. The banks failed to manage obvious risks around confidentiality, conflicts of interest and trading conduct.
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According to the regulator the banks shared information about clients' activities which they had been trusted to keep confidential and attempted to manipulate G10 spot FX currency rates.
Today's fines are the largest ever imposed by the FCA, or its predecessor the Financial Services Authority (FSA), and this is the first time the FCA has pursued a settlement with a group of banks in this way. Large fines have also been imposed in relation to the FX abuse by Swiss and US regulators.
Martin Wheatley, chief executive of the FCA, said:"The FCA does not tolerate conduct which imperils market integrity or the wider UK financial system. Today's record fines mark the gravity of the failings we found and firms need to take responsibility for putting it right.
"They must make sure their traders do not game the system to boost profits or leave the ethics of their conduct to compliance to worry about. Senior management commitments to change need to become a reality in every area of their business.
"But this is not just about enforcement action. It is about a combination of actions aimed at driving up market standards across the industry. All firms need to work with us to deliver real and lasting change to the culture of the trading floor. This is essential to restoring the public's trust in financial services and London maintaining its position as a strong and competitive financial centre."
The FCA will be holding a press conference about the fines this morning at 9am.