It was founded in 1990, as the successor of the Socialist Union of Working People of Slovenia (which in January 1990 had broken away from its Yugoslav parent organization and became an independent association).
The founding conference of the party was held in Ljubljana on June 9, 1990.
[2][3][4] The party participated in the first free parliamentary election in Slovenia that took place in April 1990, obtaining 58,082 votes (5.37%) and five seats.
Differently with the reluctance of the rest of the opposition regarding the government's plans for secession from Yugoslavia, the Socialist Party openly supported Slovenia's independence from the early period: in 1990, they were the first party to propose a referendum on Slovenian independence.
In the subsequent 1992 parliamentary elections, the party failed to win representation: it obtained 32,696 votes (2.75%) and no seat in parliament.