The affiliation of CS with the PT was not to last and by late 1991 the leadership of the latter was concerned at the activities of some PT factions particularly CS. This situation arose due to the involvement of CS in extra-parliamentary struggles and deepened in 1992 as the CS campaigned against the government of Fernando Collor de Mello and the International Monetary Fund. The situation continued to deteriorate and in June CS was expelled from PT. In response the CS formed the Revolutionary Front which at a Congress in April 1993 became the PSTU with the fusion of CS into the new party alongside a number of smaller groups including Democracia Operária (RS), the PFS, MSR (PE), Liga and the CS. 21 of April Movement.