The misconduct continued until October 2013, months into the launch of the FCA's probe and more than a year after the first settlement over Libor – the London interbank offered rate – which led to $6bn of fines.
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Martin Wheatley, the chief executive of the FCA, one of the regulators which imposed the forex penalties, is likely to welcome these moves. He said after this week's settlement that firms should review their bonus plans and claw back payments already made.
The FCA and the Prudential Regulation Authority, the Bank of England's financial regulatory arm, have to approve bonus plans for bankers based in the UK. Senior officials have made clear that misconduct should affect the award of incentives.
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RBS has already suspended the vesting of bonuses for 19 traders as a precaution.
A UBS spokesman said: "Naturally, where we find acts of wrongdoing, our policy to claw back and not pay out will come into effect." The other banks declined to comment.
JPMorgan was one of the only known examples of a bank using such clawback powers when it demanded back trader bonuses in the wake of its multibillion "London Whale" trading loss in 2012.
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Other penalties could be looming for forex traders involved in the scandal. The UK's Serious Fraud Office and the US Department of Justice have also launched criminal probes against individuals.
George Osborne, the chancellor, pledged on Friday to provide the SFO with all the funding it needs to make its own inquiries into the forex scandal. In a letter to the Attorney General, he said the Treasury would provide any extra cash needed for the probe.
The SFO asked last month for £26.5m worth of "blockbuster funding" to cover the additional costs of other cases, including into alleged Libor-rigging, alleged overseas corruption by Rolls-Royce, Barclays' arrangements with Qatar, and costs related to a damages claim by the Tchenguiz brothers.
The Treasury has not turned down previous requests for blockbuster funding.