The president of the National Front, a right-wing Eurosceptic party, issued the warning to Jean-Claude Juncker, the president of the European Commission after branding his state of the Union speech to MEPs at the European Parliament in Strasbourg, France, “insipid”.
Expressing his “regret” at the historical Brexit vote, Mr Juncker insisted the EU is “not at risk”.
But he warned the next 12 months were a “crucial time to deliver a better Europe”.
The former Luxembourg Prime Minister added: “The scope in which we cooperate together is far too small.
Marine Le Pen branded his speech “faulty” as she spelt out the death of the European Union
“This is basically almost like a funeral for the European Union, but perhaps we should admit there was a very good point on humor where you said you were the hero of combatting fiscal optimization for multinationals.
“But really, you haven’t been paying attention to the ambition of people in the European Union to reestablish and retake their sovereignty and their independence.
“Brexit has really broken a taboo. The Brits have shown us that you can leave the European Union and you can come out better.
“The catastrophic visions were just a lie. The UK is doing quite well, the shock that you wanted to see has now turned into trust, everybody thought there was going to be apocalypse falling on the UK but that didn’t happen.
“You’ve shown a disdain for the referendum, so what are you protecting us from? Freedom? Democracy?
“It is time to move on and I think that people need a project for the future. Let’s be democrats, finally, and let the people decide.”
As she received praise from other members of the European Parliament, she was asked whether she will campaign for “Frexit”.
Ms Le Pen responded: “Well, with respect to democracy I think a referendum is the best application for us.
“Over the past four years, I have said that I will be organizing a referendum so French people can express themselves on the issue of France leaving the European Union.”
Recent polls have placed Ms Le Pen as one of the front-runners for next year’s presidential race, although she faces a packed contest which will also include former leader Nicolas Sarkozy.