"QE is all around us and optimism is in the air," Varoufakis told a business audience in Italy. "At the risk to sound the party pooper ... I find it hard to understand how the broadening of the monetary base in our fragmented and fragmenting monetary union will transform itself into a substantial increase in productive investments.
"The result of this is going to be an equity run boost that will prove unsustainable," he said.
Varoufakis reiterated that the new Greek government was ready to time its promised anti-austerity measures in a way that helped negotiations with European Union partners over the disbursement of financial aid.
"We never said we're going to renege on any promises, we said that our promises concern a four-year parliamentary term," he told reporters on the sidelines of the conference.
"They will be spaced out in an optimal way, in a way that is in tune with our bargaining stance in Europe and also with the fiscal position of the Greek state," he said.
Athens needs to agree with creditors on a revised package of measures in order to access funds pledged to it from the euro zone and the International Monetary Fund under a four-month extension of its bailout programme.
Speaking at the same conference on Friday, Varoufakis expressed confidence an agreement would be reached by April 20th.