The organization had presence and influence in the labor movement of Vallès Oriental, Tarragona, Almussafes and in the construction sector of Madrid, Illes Balears, Córdoba, Granada and Camp de Morvedre.
The first Secretary General of the OIC was Dídac Fàbregas, who used the "nom de guerre" Jerónimo Hernández.
On January 11, 1978 he resigned from his position as Secretary General due to a majority vote in the federal executive in which the fusion with the Communist Movement (MC) was approved.
Four days later in a letter to the Federal Executive Commission Dídac Fàbregas renounced to his membership of the party.
In 1979 the OIC was finally absorbed by the MC, which led to an important part of its former founders and many historical leaders leave the organization, later joining the majority of them the PCE-PSUC or the PSOE.