The City firm run by former Conservative party chairman Michael Spencer is expected to learn on Wednesday that US authorities are charging former or current employees in connection with the Libor-rigging scandal.
The regulatory action against Icap would follow the £290m fines Barclays paid to US and UK regulators, Royal Bank of Scotland's £390m and the £940m penalty levied on the Swiss bank UBS.
In May Icap said three employees were on administrative leave and another suspended in connection with Libor rigging and the firm is now expected to pay under £70m in fines. The broker declined to comment further on Wednesday.
The company has insisted that none of its senior management were ever aware of or involved in improper activities about manipulating Libor, a benchmark interest rate used to price £200 trillion of financial products around the world.
A year ago Spencer said the investigations in to Libor were not a high concern to the firm, which acts as a broker between major financial firms in the money markets. Icap was not involved in setting Libor rates directly.
He later said it was disappointing that the City's reputation was being damaged by "the apparently stupid and venal activities of a few individuals".
The Wall Street Journal said US prosecutors would announce charges against past or present employees as early as Wednesday.
The way Libor is set and regulated has now been overhauled and will be overseen by the body that runs the New York Stock Exchange rather than the British Bankers' Association.
The European Union has also unveiled plans to toughen up rules to police Libor but stepped back from stripping London of responsibility for regulating benchmark rates.
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