Two years later in Paris, Joseph's son, Prince Stanislas Poniatowski (1835–1908), married Louise Le Hon, generally reputed to be the daughter of Countess Le Hon (née Fanny Mosselman) by Charles, Duke de Morny, the illegitimate son of Charles Joseph, comte de Flahaut by Hortense de Beauharnais, sometime Queen consort of Holland as well as the adopted and step-daughter of Napoleon I; thus Louise Le Hon (as a granddaughter of Napoleon III's uterine half-brother) was a niece of the Emperor of France at the time of her marriage to Poniatowski, who was appointed the emperor's aide-de-camp.

[citation needed] In August 1975, he sent the French military of France to repress the nationalist rebellion in Corsica by Edmond Simeoni, who had illegally occupied a wine cave in Aleria.

Two gendarmes were killed during the assault, leading him, along with Chirac, of being accused of a large part of the responsibility in the violence that hit Corsica.

The satirical newspaper recalled that de Broglie had been treasurer of the Independent Republicans and tied to the Matesa scandal, which allegedly funded the RI.

Soon after the affair and the failure of the right wing at the March 1977 municipal elections, Poniatowski quit the Ministry of Interior and would not be called again as minister.

Poniatowski was a founding member in 1978 of the Union for a French Democracy (UDF), the liberal and Christian democrat party that backed Valéry Giscard d'Estaing and tried to rival Chirac's neo-Gaullist Rally for the Republic (RPR).

Poniatowski approved in September 1983 the merger of the electoral list RPR-UDF with the far-right National Front (FN), a party headed by Jean-Marie Le Pen, during the partial municipal election of Dreux.

Three years later, he participated to the right-wing party of Charles Millon, who was excluded from the UDF for the same reasons as Poniatowski, and they founded the Droite libérale-chrétienne (Liberal-Christian Right), which continued to ally itself with the National Front.