The Front National leader, who looks set to storm the first round of voting after running as an outsider candidate, called the UK’s decision “formidable”.
But French presidential hopefuls Emmanuel Macron and François Fillon mocked her statements, laughing them off as Ms Le Pen stood her ground.
It came as Mr Fillon attempted to discredit the far right firebrand’s Eurosceptic views.
Mr Fillon said: “You cannot pull out of the euro which is supported by a European Union that has its faults but is there.
Le Pen accused French leaders of using a 'Project Fear' approach
“You can’t pull out of the European central bank, thanks to which we have very low interest rates, to go off on an adventure that would lead to a new currency, inflation and devaluation which would be ruinous for borrowers and lenders.”
But Le Pen defended her anti-EU stance – and accused her opponents of using the same “project fear” approach used during the EU referendum and Donald Trump’s ascension to the White House.
She said: “Mr Fillon you are just fuelling people’s fear. It’s exactly what people did against Donald Trump.”
Meanwhile Mr Macron defended the fear mongering approach, and claimed Brexiteers “disappeared” after the successful vote to break out of the bloc.
The Front National leader's opponents attempted to shout her down Things you didn't know about Marine Le Pen Mon, February 20, 2017
Marine Le Pen is a French politician who is the president of the National Front, a national-conservative political party in France and one of its main political forces.
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Described as more democratic and republican than her nationalist father, she has led a movement of "de-demonization of the Front National" to detoxify it and soften its image
Attacking Le Pen, he said: “The people who are in your position beforehand did not stick around what happened afterwards I completely agree with what Mr Fillon said he is completely correct.
“The people who were in your shoes before Brexit who said that ‘the world is going to be great’ – they disappeared the day after the vote.”
But the Front National leader, shouted down by her opponents and mocked by the French audience, claimed the results of the EU referendum were “fantastic”.
She added: “It is fantastic. It’s really great what they’ve done in the UK.
“The results in Great Britain are formidable. Their growth is double our growth.”
Macron defended Fillon's europhile stance
Earlier in the debate Le Pen vowed she will not be Angela Merkel’s lapdog if she becomes president of France as she launched a scathing attack on the EU.
Ms Le Pen said: “I want to be the president of the French Republic, truly. I am not going to become involved in a vague region in Europe. I don’t want to be the vice-chancellor of Madame Merkel.
“I don’t want to be the salesperson for multinational or large group. I want to be president of the French Republic which respects article five which states the president guarantees national sovereignty and territorial integrity.
“It is not just empty words. Thousands of French people died for our national independence.”