It became a member of the Communist International , and followed a Marxist-Leninist line under the leadership of Maurice Thorez. In response to the threat of fascism , the PCF joined the socialist Popular Front which won the election, but it did not participate in government. The PCF participated in the provisional government of the Liberation from to , but for the next 30 years was excluded from government despite consistently winning more than 20 percent of the vote in elections. In , the PCF claimed to have had , members, 70, of whom had paid their membership fees.
The s saw a number of splits within the party over relations with other left-wing parties and over adherence to Comintern 's dictates. The party entered the French parliament , but also promoted strike action and opposed colonialism , a position that was isolated in the French political landscape at the time.
The Intercolonial Union, created in , brought together activists from the French colonies around demands for political equality the right to vote and social equality "equal pay for equal work".
The communists thus called for fraternization with the Moroccan insurgents during the Rif War — and to the evacuation of Morocco by the French army, they called for an end to the fighting and the independence of French Syria during the Great Syrian Revolt of —, and denounced the festivities of the centenary of the colonization of Algeria, organizing in particular a campaign to boycott the Paris Colonial Exposition The party was organized around leaders who were mostly from the working class, setting up training and promotion schemes and encouraging the presentation of working-class candidates in elections.
The railroad worker Pierre Semard had been secretary general of the party from to Semard sought party unity and alliances with other parties; but leaders including Thorez party leader from to imposed a Marxist-Leninist line from the late s. It was the only political party in France to denounce this agreement. After the German invasion of the party began to organise opposition to the occupation.
