An Iranian newspaper has called Carla Bruni, France's first lady, a "prostitute" after she attacked Iran's plan to stone a woman to death.
The president's wife is part of a campaign to save the life of 43-year-old mother of two, Sakineh Mohammadi Ashtiani.
Ashtiani is accused of cheating on her husband and then helping to kill him.
She is now facing capital punishment for her crimes.
France has urged the European Union to threaten new sanctions over the case.
'Lived and loved'
There were marches in several French cities this weekend in support of Ashtiani.
The protest has gained momentum with both the President and his wife voicing support.
Ms Bruni wrote an open letter to the Iranian mother of two.
"Why shed your blood and deprive your children of their mother?" she wrote.
"Because you have lived, because you have loved, because you're a woman, and because you're an Iranian? Everything within me refuses to accept it".
The responding editorial in the Iranian newspaper Kayhan titled "French prostitutes join the human rights protest" accuses the French first lady of being a hypocrite.
It draws attention to a chequered love life and her numerous relationships with high-profile celebrities.
It also singles out the French actress Isabelle Adjani, who is friends with Carla Bruni and who is also calling for Ashtiani's release.
Kayhan, a state-run newspaper, acts as a mouthpiece for the country's conservative Islamic regime.
But state television has also joined in, saying Ms Bruni was trying to justify her own "immorality".
As yet, the Elysee Palace says it has no formal reaction to slurs in the Iranian press.