During the violent years of the 1980s in the Basque Country, mid- and high-ranking party officials held government positions in Spain and the region, as civil governors.

The Basque nationalist left—Herri Batasuna and related groups—denounced during that period the collusion of the party with police abuses—especially pointing to the Guardia Civil—and in early 1984 blamed directly the Socialists for the state terrorism of the GAL death squads (1984-1987).

[7] Ricardo Damborenea, head of the party in Biscay, even confessed in a press release to his involvement in the criminal pursuit in the early 1990s.

All of them have been released from prison much earlier than their due term without apologising for their illegal actions; Damborenea currently gets a substantial monthly allowance from the Spanish state.

The fusion of the two groups was made possible by the split of Basque Left from EE: prepared by the leadership of Nicolás Redondo Terreros (1998–2002), it was confirmed with the mandate of Patxi López in 2002.