It was founded in 1950 as a socialist, social democratic, republican, and laic split from the Italian General Confederation of Labour (CGIL).

The resulting association, known as the "United CGIL", was established to unify all the Italian workers under one banner, without regard to their political and religious views.

The pact united the three leading political movements (communist, socialist, and Catholic) in the name of workers' rights and the ongoing fight against fascism.

[5] Unwilling to continue cooperation with increasingly militant socialists, on September 15, 1948, a group of Catholic trade unionists, consisting of Republicans and Social Democrats, split from CGIL.

[citation needed] In the end, only the FIL leadership joined the LCIGL (which changed its name to the Italian Confederation of Workers' Trade Unions on April 30, 1950).

The bulk of the rank and file membership resolved decided to form a new union, independent from the politics and foreign influence which had sundered the CGIL and FIL.

On 5 March 1950, in the Casa dell’Aviatore (Aviator House) in Rome, 253 delegates from the now defunct FIL congress participated in the foundation of the Italian Labour Union (UIL).

Due in part to resisting American interests by refusing to merge with the LCIGL, the union was denied political partnership and funding for several years.

[citation needed] The federation came to an end in 1985 when a law[12] issued by the Bettino Craxi cabinet divided the member unions.

The CISL and UIL, led by Pierre Carniti and Giorgio Benvenuto, and factions within the CGIL (especially those influenced by Ottaviano Del Turco) aligned themselves with the government's position against a referendum.