The Workers' Commissions since the 1970s has become the largest trade union in Spain. It has more than one million members, and is the most successful union in labor elections, competing with the Unión General de Trabajadores (UGT), which is historically affiliated with the Spanish Socialist Workers' Party (PSOE), and with the anarcho-syndicalist Confederación General del Trabajo (CGT), which is usually a distant third.

The Unión General de Trabajadores is a major Spanish trade union, historically affiliated with the Spanish Socialist Workers' Party (PSOE).