Most notably, the All India Forward Bloc under Sheel Bhadra Yagee joined USOI.
Ahead of the 1952 Indian general elections, USO comprised All India Forward Bloc, Sarat Chandra Bose's Socialist Republican Party, Bolshevik Party of India, Indian National Army, People's Movement and others and independents.
USOI came to an understanding with Communist Party of India to form an anti-Congress front in West Bengal.
Attempts were made to involve RSP in this front, but the negotiations ahead of the elections failed.
In total, USO fielded 72 candidates in the West Bengal assembly and CPI 71.