Draghi also defended Blackrock's role as an adviser on the ECB's purchasing program for covered bonds and ABS (asset-backed securities). The U.S. investment firm was active during the sub-prime crisis of 2007, when major banks collapsed after loading up on securities backed by mortgages which then defaulted in large volumes.
"We are using Blackrock to help us design our program, which is nothing strange at all," said Draghi. He added that the U.S. Federal Reserve had also hired investment management firms to advise them about QE.
"Their function is purely advisory," said Draghi. "We have been extremely careful about containing any conflict of interest."
TLTROs and private asset purchases are some of a number of stimulus measures recently announced by Draghi that have left markets wanting more. This has led to a growing number of economists expecting the ECB to launch a Federal Reserve-style quantitative easing (QE) program.
On Monday, Draghi said the bank stood ready to use "further additional unconventional instruments" if necessary. He has stated his willingness to do so repeatedly, fueling hopes of QE.
A team of analysts at Barclays, led by Philippe Gudin, are now so sure the central bank will have to start buying up government bonds that they argue a QE program is the base-case scenario for the euro zone.
"Increasing the ECB's balance sheet by up to 1 trillion euros to its 2012 size is unlikely to be achieved via TLTROs, ABS (asset-backed securities) and covered bond purchases alone," the bank said in a research note on Friday. Barclays believes the new measure will most likely be implemented by the first quarter of 2015.
Read MoreDraghi: ECB to purchase asset-backed securities
"Second, we believe that the risk of too long a period of low inflation is higher than the ECB's inflation projections imply, while the growth outlook has significantly deteriorated and remains subject mainly to downside risks, especially for France and Italy," the bank added.