On 10 May 1979, he won the by-election in what was then Rangpur-1 (the current Nilphamari-1 constituency) as the candidate of the Bangladesh Nationalist Party (BNP), after the seat was left vacant due to the death of his father, Mashiur Rahman. On 1 January 1986, when the Jatiya Party (E) was formed, he was a founding member and made the organizing secretary of the party.[6] Later that year, during the general election, he ran in both the Rangpur-3 and Nilphamari-1 constituencies as the Jatiya Party (E) candidate, going on to win both seats. Consequently, in line with the constitution, he surrendered the Nilphamari-1 seat (triggering a by-election in the constituency) and went on to represent Rangpur Sadar (Rangpur-3) in parliament.[7][8][9]
From the mid to late 1980s, Swapan served as a cabinet member of President Ershad's Jatiya Party (E) government, holding many different portfolios. Throughout this period, he was made responsible for the Ministry of Youth and Sports (1984–1985),[10]Ministry of Civil Aviation and Tourism (1985–1986),[11] and the Ministry of Housing and Public Works (1986–1988).[12]
Swapan died on 23 August 2009 in a hospital in Dhaka, Bangladesh. His janaza (funeral prayer) was held at the South Plaza of the Jatiya Sangsad Bhaban (National Parliament House) after which he was taken to his ancestral home in Dimla, Nilphamari where another janaza was held before he was finally laid to rest at his family graveyard in Dimla.[1]