His older sister Jacqueline, better known as Jacquetta of Luxembourg, married John of Lancaster, 1st Duke of Bedford, and Louis was initially a supporter of the Lancastrian cause in the English Wars of the Roses.

After this, he was persistently disloyal to the King, conspiring with Charles, Count of Charolais, and with Edward IV of England (the husband of his niece, Elizabeth Woodville).

The final treason came in 1474 when Saint-Pol approached Charles the Bold, Duke of Burgundy, who had already entered into a compact with Edward IV of England to dismember France in a renewal of the Hundred Years' War.

The scheme envisaged the murder of Louis and the sub-division of France between Saint-Pol, the Dukes of Burgundy, Brittany, Bourbon and Nemours, the Count of Maine and King Edward.

Philippe de Commynes, the chief chronicler of Louis' reign, was to write that Saint-Pol had been "abandoned by God because he had tried with all his might to prolong the hostilities between the King and the Duke of Burgundy."