Florian Philippot, Front National deputy leader, said he would resign if the party ignored its core policy to restore the franc as the national currency.
Mr Philippot said: “If we carry on with this currency there will never be any solution to our unemployment. Promising the French economic patriotism but staying in the euro means lying to the French.”
The populist far-right party could implode as the defeated presidential candidate desperately tries to adapt the group after admitting her hostility to the euro had played a big role in her defeat to Emmanuel Macron.
French polls show that more than 70 per cent of the public want to stay in the single currency. The party is worried the prospects of gaining seats at the parliamentary election next month are fading quickly.
Nicolas Bay, General Secretary of the Front National, condemned Mr Philippot and accused him of blackmail.
Mr Philippot, the Front National’s deputy leader, launched a controversial new nationalist political movement dubbed Les Patriotes.
Mr Philippot previously announced that the newly founded far-right movement will strive to “follow through” on Marine Le Pen’s concession speech promise to “transform” the party.
Ms Le Pen did not say whether she would change her party’s name, but said she would reach out beyond the current Front National and reconstruct the French political landscape around a “patriots” versus “globalists” divide.
The 48-year-old is fighting to reassert her leadership while aiming to make a political comeback and stand in France’s upcoming parliamentary election.
A senior Front National official told a political weekly newspaper: “Marine is worn out and cannot allow herself another defeat.”
Ms Le Pen announced she will stand to become an MP in Calais at June’s elections.
She said: “Yes, I will be a candidate… this battle of the legislative elections is fundamental.”
She added she had a “strong emotional relationship with the inhabitants of the Pas-de-Calais mining area”.