After joining Anusheelan Samity, Comrade Promode shifted his political activities to Calcutta. He was arrested in connection with the famous Machua Bazzar Bomb Case in 1929 along with a number of others like Satish Pakrashi, Sudhansu Dasgupta and Satyabrata Sen. Some of them were convicted and sentenced to imprisonment, while there was not enough evidence to convict Comrade Promode. But he was detained under the Bengal Criminal Law Amendent Act. He was for eight years in various jails in Bengal and in the Deoli detention camp. He was released in 1937.

Comrade Promode earned his membership in the CPI on May 1, 1938, and began working among the dock labour in Calcutta. He worked as the Secretary of the Calcutta District Committee of the Party and was underground for some time during the period of the Second World War. Later he was arrested and was released after the legalisation of the Party in 1942.

It was then that Comrade Promode organised the press of the Bengal Committee of the Party and the publication of its first Bengali Weekly Jan Yudh and later Swadhinata daily. During the attack on the Party in 1948-51 immediately after India attained Independence, Comrade Promode worked underground for some time and was arrested and detained in jail for the rest of the period.

After he came out of jail in 1951, he took a leading part in reorganising the Party in West Bengal and resuming the publication of Swadhinata daily.

Comrade Promode was elected Secretary of the West Bengal State Committee of the Party at the Burdwan State Conference prior to the Sixth Party Congress in Vijayawada in 1961. He remained in that post till his death. He was elected to the National Council of the CPI at the Fifth Amritsar Congress of the Party in 1958 and to its Central Executive Committee in 1961.

The inner-Party struggle against revisionism which had begun on the eve of the Fourth Congress of the Party reached a climax at the Vijayawada Congress. Comrade Promode was one of the leading comrades who paticipated in this struggle against revisionism since the Sixth Congress. Later when Naxalite Left-adventurism came on the scene and the Naxalites began their annihilation campaign with the CPI(M) as their main enemy, the Party in West Bengal under the leadership of Comrade Promode fought a bitter political battle to expose the Naxalite ideology and isolate and defeat the Left -adventurists and to defend the Programme of the Party and its organisation.

At the time of the India-China war in October 1962, a section of the leadership of the CPI was arrested and detained. Comrade Promode was one of them. From inside jail, Comrade Promode and other leading comrades guided the party members in West Bengal in the struggle for Marxism-Leninism and proletarian internationlism. He was among the last to be released in West Bengal in 1964. He was in the leadership which organised the Tenali Convention which gave the call for the Seventh Congress Party. Just a few days before the Seventh Congress, Comrade Promode and other West Bengal leaders of the party were arrested and detained. After the Congress, the Party in the rest of the country was also attacked by the Congress rulers and most of the Central, State and district leaders were detained. From inside jail, Comrade Promode and others again gave guidance to consolidate the achievements of the Seventh Congress and strenghthen the Party. He was elected to the Polit Bureau of the CPI(M) at the Seventh Congress, a post which he held till his death.

Comrade Promode Dasgupta was a dedicated Communist who lived the life of a revolutionary facing all difficulties, sufferings and sacrifices for more than five decades. He led the Party in West Bengal through various vicissitudes, defending it in periods of direct attacks as during the years of the semi-fascist terror, while at the same time utilising all the legal opportunities that were available. He played a major role in forging and strengthening the Left Front in West Bengal. He died in Beijing on November 29, 1992.