He said the ECB was "technically ready" to take the interest rate on its deposit facility into negative territory - in other words, to charge banks to park their cash with the central bank.

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Eurodollar futures and options, where investors hedged or speculated on the interest rate paid on a 90-day deposit of a dollar overseas, were half of the Merc's business, with 1.5 million contracts traded per day.

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However, when central banks pay interest on reserves or a deposit facility, this interest rate is rarely the one used to set the target for short-term private sector borrowing rates.

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The most the ECB has done to try and encourage more lending is cut its overnight deposit rate, in other words paying less interest on money it borrows from banks overnight.

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