Socialist Party has been the name of several political parties in India, all of which have their roots in the Congress Socialist Party formed during the freedom struggle. (The Samajwadi Party is also a modern-day party whose first name in Hindi means "socialist".)
The former Congress Socialist Party
The original Socialist Party had its roots in the Congress Socialist Party (CSP), the socialist caucus of the Indian National Congress, which fused in 1948 with the Bolshevik-Leninist Party of India, Ceylon and Burma (BLPI). Hector Abhayavardhana of the BLPI became General Secretary of the new party. The Socialist Party was founded not long after India's independence when Jayprakash Narayan, Basawon Singh (Sinha), Acharya Narendra Dev led the CSP out of Congress. At the time, Congress's leader Jawaharlal Nehru was a democratic socialist whose sentiments were widely admired by the rank and file of the CSP, but they objected to his apparent unwillingness to act decisively in favour of democratic socialism or to renounce his dependence upon the conservative Hindu wing of the party represented by Sardar Vallabhbhai Patel or C. Rajagopalachari.
Indian Socialist Party
Despite Jai Prakash Narayan's personal popularity, the Socialist Party won only 12 seats at the 1951 Indian general election, and its electoral fortunes did not improve. The SP merged with the Kisan Mazdoor Praja Party, which had recently been formed by J.B. Kripalani, to form the Praja Socialist Party.
Praja Socialist Party
The Praja Socialist Party was an Indian political party in existence from 1952 to 1972. It was founded when the Socialist Party, led by Jayprakash Narayan, Acharya Narendra Deva and Basawon Singh (Sinha), merged with the Kisan Mazdoor Praja Party led by J.B. Kripalani (formerly a close associate of Jawaharlal Nehru). A section led by Rammanohar Lohia broke from the party in 1955, resuming the name "Socialist Party".
In 1974 and 1975, JP led satyagrahas against the corrupt government of Indira Gandhi and called for a 'Total Revolution' in the countryside. In response, Indira declared the two-year State of Emergency under which her own power was consolidated and JP was jailed.