Benoit Coeure, a member of the ECB's governing council believes that the "evil genie" of a eurozone country possibly leaving the monetary union was released during the recent negotiations between Greece and its international creditors.

While a third Greek bailout has been agreed, he warns that Europe has to make it clear that a country leaving the currency is not an option.

Speaking in Paris, he said: "The recent negotiations concerning Greece have let the evil genie of a country exiting the euro area (even temporarily) out of the bottle. The exit of a member country would inevitably lead economic actors to wonder who would be next, with all the potential destabilising effects that such speculation could entail."

He continues, "The genie will not be put back in its bottle once and for all until it is clear that such a risk will not rear its head again."

Mr Coeure warns that he believes that the possibility of the euro project failing has been overstated by eurosceptics.

During the final stages of Greece's negotiations official European documents proposed that Greece could temporarily leave the euro to rejoin at a future date.

When the euro was designed no legislation, or mechanisms were built to deal with the possibility of a country leaving the Union.