Citigroup said Rohan Ramchandani, its former head of European spot trading who was already on leave, had left the bank, a departure that comes amid a global probe into the fixing of foreign exchange rates.
Citigroup declined to give further details about the circumstances of Mr Ramchandani's departure.
At least 12 foreign exchange traders at global banks have been suspended amid probes into possible manipulation and collusion in foreign exchange markets, where $5.3tn is traded every day. None of these traders have been accused of wrongdoing.
UK, Swiss and US authorities, with the help of regulators in Hong Kong, are investigating at least 15 banks including Barclays, Citigroup, Deutsche Bank, Goldman Sachs, HSBC, JPMorgan, Morgan Stanley, Royal Bank of Scotland, Standard Chartered and UBS. Internal reviews are also under way. No charges have been brought by authorities.
Mr Ramchandani was a member of the Bank of England's foreign exchange joint standing committee chief dealers' subgroup, a forum for banks and brokers to discuss market issues.
The global probe is the latest to focus on benchmark rates after investigations into the Libor interbank lending rate, Isdafix interest rate swaps and the oil spot markets, which have hurt bank earnings and tarnished their reputations.
Banks are searching reams of instant chat messages and emails to look for instances of wrongdoing. Several banks including Citigroup, Barclays and RBS have banned the use of most group chat rooms, that allow traders to confer with other traders from several institutions at once.
Mr Ramchandani was part of a specific chatroom that counted some of the most influential traders in London as its members. The group also included Richard Usher, a former RBS trader who moved to JPMorgan as the head of spot forex trading in 2010, and Matt Gardiner, who joined Standard Chartered after UBS and Barclays.
The Wall Street Journal reported that Mr Ramchandani had been fired by the bank earlier on Friday. Mr Ramchandani could not be reached for comment.
While the foreign exchange market is large, the $2tn spot market is dominated by a group of fewer than 100 individual traders and a small group of the big banks.
The main rate for foreign exchange markets is the WM/Reuters 4pm fix. Mutual funds around the world trade currencies based on the fix.
While collusion is illegal, it is less clear if front-running or "pre-hedging" qualifies as criminal, a misconduct or not an offence at all, lawyers have said.
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