Parizeau had called for the CPC and PCQ-PCC to demand the immediate independence of Quebec; he was swiftly rebuked by other provincial party leaders and the federal leadership.

While the Catholic Church, particularly after the Russian Revolution in 1917, waged an active campaign from the pulpit against trade unionists, leftists and Communists, Marxist discussion already had taken hold in Quebec by the early 1920s.

In 1921, Buller became a founding member of the underground Communist Party of Canada (CPC) which united other radical labour activists from Nova Scotia to BC.

While the request was rejected by the international and the Communists were instructed build a united party, the Comintern it did not ignore the special national situation that presented itself in Quebec.

(The internationalist commitment of the CPC would be important in helping the party better understand Quebec's situation and eventually adopt a policy supporting the right of self-determination and sovereignty, up to and including separation.)

By 1927, the CPC had begun to also focus on political activity among French-Canadian workers in Quebec, recruiting and training new cadres for the Party.

In July 1930, during the Great Depression, the party stepped up its visibility by presenting E. Simard, a blacksmith, as the first Communist candidate in the 1930 Canadian federal election running in Maisonneuve, Montreal.

Simard's programme characterized the Communist platform of the time, demanding employment insurance reform, public health care, and immediate action on the unemployed.

The party organized a demonstration against the arrest at Viger Square, the police brutally disperse the hundreds of protesting workers.

The CPC organized an assembly of the League against War and Fascism in Montreal, when 600 people came out to hear Lilian Mendelssohn, Joe Wallace, Fred Rose, Maurice Armstrong and a young student who had just returned from France – Stanley Bréhaut Ryerson.

In another documented rally, as many as 4,000 people gathered at St. Jacques Market to hear Joe Wallace, John Boychuk, Becky Buhay, Paul and Tom McEwen and were brutally dispersed by police.

Leader Évariste Dubé visited the USSR on a special party delegation, as did radical medic Norman Bethune with a group of progressive Canadian doctors.

S. Larkin, J. Bedard, C. A. Perry, L. Dufour and Ms. Lebrun helped build various clubs and groups of factory workers like the United Lorimier Unemployed League St. Henri.

Labour demands were also front-and-centre in October 1935 when the CPC, now de-criminalized and able to operate legally, ran in the federal election: leader Fred Rose got 3378 votes in Montreal-Cartier, while CA Perry got 1,012 in Saint-Denis.

Abandoning the 'department' model, an executive committee of the Quebec section of the Communist Party was formed including Évariste Dubé (Chairman), S. B. Ryerson (secretary), Fred Rose, Emile Godin Alec Rosenberg, Samuel Emery.

In May 1938, approximately 4,000 people attended a meeting of the Communist Party unit and the Co-operative Commonwealth Federation in the Mont-Royal arena in Montreal.

In 1941, at a meeting in Montreal, Guy Caron of the Communist Party and Jean-Charles Harvey of Le Jour newspaper spoke to 6,000 people to support the war effort against the fascists.

On 15 October, dissatisfied with the explanations provided by Buck, Guy Caron resigned from the LPP with five other members of the provincial committee: Ken Perry, Harry Gulkin, Norman Nerenberg, Frank Arnold and Pierre Gélinas.

The project to create a mass party of workers from unions was subject to closed debate on the floor of Congress of the Quebec Federation of Labour in 1975.

Given the lack of enthusiasm on the part of unions to promote such a project, which was increasingly seen as being harmful to the chances of PQ to finally beat the Liberals, and to the difficulties within the groups Left can agree because of the extreme partisanship that existed then the idea died a natural death.

The old members of the PCQ who left the party a few years before re-joined, and although recognizing differences over the national question they decided to work together.

A few years later the party helped bring together different tendencies in the left to form the Union of Progressive Forces (UFP) which became Québec solidaire.

A few months later, in a rather unexpected move, the SDP calls on the DMP effect coming as a special guest, to attend their next conference, in order to enforce its vision of the unity of left forces.

The UFP in turn merged with the political movement Option citizen in 2006 to form the party Québec solidaire (QS).

Although his Quebec nationalist point of view held a majority at the PCQ's convention of April 2005, who was granted voting rights was highly disputed.

The non-registered CPC-aligned PCQ held a new convention which restarted a communist French-language periodical, Clarté, and later opened an office and small reading room, launched an active website, and re-affiliated with Quebec Solidaire as an organized group.

They work closely with the youth and student organization, the "Ligue de la jeunesse communiste du Quebec".

The PCQ-PCC participated in the 2007 elections under the banner of Quebec Solidaire, focusing on the campaign of one candidate in Acadie (bumping out the leader of the nationalist PCQ).

[5] In 2002, the Communist Party joined the Union des forces progressistes with some of its members running as UFP candidates in the 2003 Quebec general election.