PARIS (Reuters) - A row heated up on Thursday in France’s National Front (FN) over the euro, with leader Marine Le Pen’s top aide threatening to resign if the party dropped its policy of ditching the European currency after her defeat in the presidential election.

A person holds a mask of France's National Front (FN) defeated presidential candidate, Marine Le Pen, as people gather with French and European flags near the Eiffel Tower and a banner with the message, "France tells Hate: Never Again" the day after presidential elections in the country, in Paris, France, May 8, 2017. REUTER/Pascal Rossignol

Le Pen’s heavy defeat on Sunday by centrist Emmanuel Macron has prompted soul-searching within the far-right FN with some blaming her commitment to quitting the euro zone for the outcome.

While a large majority of FN supporters back a return to the French franc, opinion polls indicate three-quarters of French voters want to keep the euro, including many older voters who fear their euro-denominated pensions could be devalued.

Echoing this view, a FN-affiliated lawmaker said Le Pen needed to learn the lessons from Sunday’s defeat and accept that the party should drop its hostility to the euro.

“For us, the question of the euro is over. The people held their referendum last Sunday. Marine must listen to that message,” Gilbert Collard, part of her inner circle, was quoted as saying in Le Parisien newspaper.

But Le Pen’s number two and the party’s vice-president, Florian Philippot, replying to an RMC radio journalist, declared he would quit the party if it abandoned its euro strategy.

“I am not here to hang on to a job at all cost and to defend the opposite of my deepest convictions. I will always fight for the independence of my country,” he said.

‘MONETARY SOVEREIGNTY’

Referring to the intense debate within the party over its line on the euro, he added: “I don’t mind the question being raised. But I think we lose a lot of credibility. Those who think we gain from this are making a mistake.”

The head of the FN Youths, Gaetan Dussausaye, told Reuters he saw no reason to challenge the FN’s stance on the euro.

“Without monetary sovereignty we cannot boost our competitiveness,” he said. “There’s no reason to change our views on this.”

The European Union was the second most important issue for voters on Sunday, according to a Harris Interactive poll, just behind jobs and ahead of security, migration, taxes and other themes.

The election offered a stark choice between Le Pen’s euroskeptic plans and those of Macron who wishes to deepen EU integration.

Macron’s victory over Le Pen, by 66 percent to 34, was more comfortable than surveys had predicted and has triggered the rare public display of disagreement among FN officials and allies over campaign policies.

Any policy adjustments will come as the party gears up for the parliamentary election in June.

After conceding defeat on Sunday, Le Pen said she would overhaul the party, without revealing what that would mean for policy.

Le Pen, during the last days of election campaigning, softened her stance to say that scrapping the euro was not a precondition of her economic policies and could take some time.

Her niece Marion Marechal-Le Pen, popular in the party and one of only four FN lawmakers, said her aunt’s change of course had come too late and failed to convince voters. Marechal-Le Pen has since said she will not run again in June’s election.

Le Pen’s estranged father Jean-Marie, founder of the party, said on RTL radio last Sunday that his daughter’s euro stance was largely to blame for her defeat.