Marion Maréchal-Le Pen, the National Front MP and niece of Marine Le Pen, the party's unsuccessful presidential candidate, is expected to announce her retirement from politics today.
Mr Le Pen said: "I had insisted that she be a candidate and she had been successful". She is one of two lawmakers in the outgoing lower house of parliament affiliated with the party.
On several occasions, Marechal-Le Pen found herself in political conflicts with her aunt and in disagreement with the policies of her party.
After the defeat, Marine Le Pen has said the National Front must be "restarted", while Philipot said the new party will have a different name. Macron defeated far-right leader Marine Le Pen handily in Sunday's presidential vote, and now must pull together a majority for his year-old political movement by mid-June legislative elections.
Marechal-Le Pen also took part in the "Manif pour tous" (Protest for all) rallies against gay marriage laws introduced in 2013 - a movement which Le Pen, who has striven to extend her party's appeal to a wider base, avoided. She said she wanted to spend more time with her young daughter and been interested in working in civil society "for some time" because she "loves the world of business".
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She added, "I am forever grateful to the people who kept me alive, President Obama, my legal team and countless supporters". Manning twice attempted suicide past year at the male military prison where she is being held at Fort Leavenworth, Kansas.
"Far beyond the pack, Marion represented a hope for the future for many activists and voters of the Front National".
"If there isn't a very serious reason for that decision, I consider it to be a desertion", Jean-Marie Le Pen, who co-founded the National Front in 1972, told Le Figaro newspaper.
Le Pen's defeat has raised questions about her leadership and she may not run for parliament in her northern fiefdom of Henin-Beaumont, where she narrowly lost in 2012.
"I do not give up political fighting definitively", she said.
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