Frans Timmermans, the First Vice-President of the European Commission, snapped at one user who said he wanted to “shut down the EU”.
The anti-EU participant put to the Dutch politician that the EU was “the biggest mistake in the history of the world”.
Reacting to the remarks, Mr Timmermans mocked the user.
He said: “Yeah big mistake – 70 years of peace, never seen before in European history, huge mistake really.
Frans Timmermans blasted Eurosceptics for having "simplistic solutions"
We’ve seen countries fight on the battlefield now disagree around the conference table – big mistake indeed!
“We’ve seen more social progress in these 70 years than ever before, we’ve seen more economic growth thanks to the internal market.
“We’ve seen countries [that used to] fight on the battlefield now disagree around the conference table – big mistake indeed!”
The EU chief then went on to blast the rise of nationalism in Europe, branding it “simplistic”.
He said: “I think we should be quite aware of the fact this is a phenomenon that has been with us for some time and will be with us for quite some time and this is a result of the fact that people have the feeling that they’re no longer really in control of their destiny.
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Frans Timmermans blasted the user for saying the EU was the "biggest mistake in history"
“That they are subject to developments worldwide where they have not enough influence in how to shape those developments.
“I believe there’s no point in just attacking the nationalists and the fanatics who propose the solutions, the simplistic solutions, of going back to the national level as a solution to all our problems.”
He questioned how going back to the “national level” would solve climate change or deal with an “aggressive” Russia.
Speaking about the future of the European bloc, he admitted it could fail if the “silent majority” did not “stand up” and commit to the project – “the biggest peace project in history”.
Mr Timmermans added: “As we stand today, this project could fail, Europe could fall apart and we have a huge silent majority of Europeans who might not be happy with European institutions.
“But they do attach huge value to the European Union as a place where European people come together to shape their future together.”