In an interview with the BBC to be broadcast on Thursday, Benoît Coeuré, executive director of the ECB, said: "In the autumn of 2011 the conditions were very dangerous … European banks were facing severe difficulties to fund themselves, to access finance, and we were very close to having a collapse in the banking system in the euro area, which would have also led to a collapse in the economy and to deflation. And this is something that the ECB could not accept."

The concern about the state of the banking system led to €1tn being lent to banks through three-year loans and came as UK banks were told to make preparations for a potential exit of countries from the single currency.