- Born on July 8, 1914 in Calcutta.
- Educated at St. Xavier's School and College and Presidency College, Calcutta. B.A Honours in English, Bar at Law from Middle Temple, London.
- Initiated to Marxism and Politics while in UK. Came in close association with Harry Pollitt, Rajani Palme Dutt,, Ben Bradley and other leaders of the Communist Party of Great Britain.
- Was a member of the India League, London, a member of the Federation of Indian Students in Great Britain, Secretary of the London Majlis.
- On return to India became a member of the Communist Party of India. As a trade-unionist, he was an important functionary of the B.A. Railroad Workers' Union and the All India Railwaymen's Federation. He was also in the leadership of several other trade union organisations.
- Between 1952 and 1957, was Secretary of the West Bengal Provincial Committee of the Communist Party of India.
- Elected to the Bengal Legislative Assembly in 1946.
- After independence, elected to the West Bengal Legislative Assembly in 1952, 1957, 1962, 1967, 1969, 1971, 1977, 1982, 1987, 1991 and 1996.
- Was the leader of the Opposition in the West Bengal Legislative Assembly from 1957 to 1967.
- Was Deputy Chief Minister of the two United Front Governments in West Bengal in 1967 and 1969.
- Took his oath as Chief Minister of West Bengal on 21st June, 1977. Headed the Left Front government in the State for five consecutive terms.
- Relinquished the office of the Chief Minister on November 6, 2000.
- Member of the Central Committee and Special Invitee to the Polit Bureau of the CPI(M)