During the World War I era, the UGT followed a tactical line of close relationships and unity of action with the Confederación Nacional del Trabajo (CNT, National Labour Confederation).

While the CNT opted for a radical confrontation with the regime and were prohibited on this account, the UGT, although in disagreement with the dictatorship, adopted a collaborative attitude in order to continue to operate legally.

[3] The influx of these workers (jornaleros) caused the union's radicalisation, and the bloody breakout of the Spanish Civil War deepened the internal fissures that resulted in the departure of Largo Caballero from the position of UGT secretary general in 1937.

The UGT and CCOO, between them, constitute the major avenues for workers' representation in modern Spain, with the anarcho-syndicalist Confederación General del Trabajo (CGT) a distant third.

The UGT declares itself to be an institution of productive workers, organized along lines of trades and liberal professions, which respects freedom of thought, leading toward the transformation of the society, in order to establish it on the basis of social justice, equality and solidarity.