In August 1947 he was appointed Commonwealth Secretary in the Ministry of External Affairs, From 1952-54, he was India's first ambassador to West Germany. He returned as Commonwealth Secretary in the Ministry of External Affairs and from 12 October 1955 to 11 April 1961 was the longest serving Foreign Secretary of India. As Commonwealth Secretary, along with V.K. Krishna Menon, Dutt was India's representative on the Political Committee at the Bandung Conference. As Foreign Secretary in the years leading up to the Sino-Indian War of 1962, Dutt was closely involved in policy formulation regarding Tibet and China. He was also involved in shaping India's response to the Suez and Hungarian crises which happened while he was the foreign secretary. He was appointed Indian Ambassador to the Soviet Union in June 1961, succeeding K.P.S. Menon. After his retirement from the Foreign Service in November 1962 he became Secretary to the President for two years. In 1964 he was appointed as the first Vigilance Commissioner of West Bengal, from 1968 to January 1972 he held the post of the Central Vigilance Commissioner. Indira Gandhi in January 1972 on short term asked him to become India's first High Commissioner to Bangladesh in 1972. Dutt retired in April 1974 protesting against the visit of Pakistani Prime MinisterZulfikar Ali Bhutto to Bangladesh.
Post retirement
Between 1964 and 1968, Dutt served as the Vigilance Commissioner of West Bengal where, appalled at how corruption had become endemic in public life, he coined the term 'speed money' noting that it had become a way of life. He chaired the Industrial Licensing Policy Inquiry Committee, known as the Dutt Committee, whose report in 1969 led to the enactment of the Monopolies and Restrictive Trade Practices Act in India. Between 1968 and February 1972, he held the post of Central Vigilance Commissioner. He also authored With Nehru in the Foreign Office in 1977.
Death
Subimal Dutt died on 2 March 1992 in Calcutta following a prolonged illness. He was 89.
Literature
1. Amit Das Gupta, Serving India. A political biography of Subimal Dutt, India's longest serving Foreign Secretary. 2. Amit R. Das Gupta, "Foreign Secretary Subimal Dutt and the prehistory of the Sino-Indian border war", in: Das Gupta, Amit R., und Lüthi, Lorenz M., The Sino-Indian War in 1962: New Perspectives : 48-67.