Marine Le Pen deliberately plagiarised parts of a speech from a former presidential candidate, as a "wink" to him and the voters she hopes to peel away in a run-off, her spokesmen have said.
Francois Fillon, the former Republican candidate, delivered the address on France's role in Europe and the world on April 15 - two weeks before Ms Le Pen's speech on Monday.
The subject is at the heart of her campaign. She promises to pull France out of the European Union and return to the franc currency, and has denounced globalisation's effects on the French economy and culture.
Three separate spokesmen for Ms Le Pen used the word "wink" to describe the extracts copied word for word from Mr Fillon. At no point in the speech did she cite him or acknowledge the source of the extracts.
"I think with part of the right, we have exactly the same vision on the national identity and independence," said Louis Aliot, National Front vice president.
Immediately after being eliminated in the first-round vote, Mr Fillon called for his supporters to back her centrist rival, Emmanuel Macron.
Mr Macron and Ms Le Pen are going after the voters of the nine other candidates knocked out in that vote, in which France's two main parties failed to make it to the second round for the first time in the country's modern history.
He is promising an ethics bill that would block office holders from conflicts of interest, nepotism and other ethical issues that have infuriated voters.
Mr Macron, who started his own political movement just a year ago, also promised he could get a legislative majority to pass the measure and others he says France needs to pull itself from the economic doldrums.
Legislative elections are in June, and whoever is president will depend on lawmakers to implement an agenda.
Mr Macron, who has pulled support from the right and the left, said candidates will have to quit their parties to run in his movement.