This article needs additional citations for verification. (July 2023)
|General Secretary||Tullio Vecchietti|
|Founded||12 January 1964|
|Dissolved||13 July 1972|
|Split from||Italian Socialist Party|
|Merged into||Italian Communist Party|
The PSIUP was formed on 12 January 1964 by a leftist section of the Italian Socialist Party (PSI). PSIUP had been the PSI's name in 1943–1947. The new PSIUP was led by Tullio Vecchietti. Other leading members were Lelio Basso, Vittorio Foa, Lucio Libertini, Emilio Lussu, Francesco Cacciatore detto Cecchino and Dario Valori. The new party attracted PSI militants who were dissatisfied with the close cooperation between the PSI and the Christian Democracy. Instead, the founders of the PSIUP favoured cooperation with the Italian Communist Party (PCI).
On 13 July 1972, following a disappointing electoral result, the PSIUP split. The majority, led by Libertini, Valori and Vecchietti, joined the PCI. The rightist minority, led by Giuseppe Avolio, Nicola Corretto and Vincenzo Gatto, rejoined the PSI. The leftist minority, led by Foa and Silvano Miniati, continued to work under the name PSIUP, and in December 1972 they established the Proletarian Unity Party (PdUP). A Posadist faction within the PSIUP published the Bollettino della sinistra rivoluzionaria del PSIUP between 1965 and 1967.
|Chamber of Deputies|
23 / 630
0 / 630
|Senate of the Republic|
13 / 315
11 / 315
- Tullio Vecchietti (January 1964 – September 1971)
- Dario Valori (October 1971 – July 1972)
- Giuseppe Impastato, anti-mafia journalist member of the party, assassinated on 9 May 1978
- Valdo Spini (January–April 1972). "The New Left in Italy". Journal of Contemporary History. 7 (1–2): 56. doi:10.1177/002200947200700103. JSTOR 259757.
- Moss, David (1981). "The kidnapping and murder of Aldo Moro". European Journal of Sociology / Archives Européennes de Sociologie / Europäisches Archiv für Soziologie. 22 (2): 265–295. ISSN 0003-9756. JSTOR 23999304.
- Lelio Basso, The Italian Left, "Socialist Register", 1966.