It was formed on December 21, 1930 by leftists expelled from the French Communist Party (PCF), together with some who had previously belonged to the left-wing of the Section française de l'Internationale ouvrière (SFIO).
Its members were known in France as pupistes, and one of its notable leaders was Alexandre Bachelet.
At one time, the party held ten seats in the Chamber of Deputies of the Third Republic.
Many of the top members of the PUP subsequently were involved with collaboration with the Axis powers during the Vichy regime.
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