Sircar went on the
Supreme Court of Bangladesh to work as a lawyer in
constitutional,
civil, and
criminal laws. In 1977, he was selected by the then President
Ziaur Rahman as a member of the Bangladesh Delegation to the
United Nations General Assembly. As a delegate, he looked after the Legal Committee and continued in this role for the next four years, between 1977 and 1980. In 1981, as a
state minister of the
Bangladesh government for the
Ministry of Foreign Affairs, he travelled to the UN to deliberate on the Middle East
peace process and
disarmament. He later attended the Non-Aligned Movement's Labor Ministers Conference in
Baghdad. He was elected to the parliament as a candidate of the Bangladesh Nationalist Party from
Panchagarh-1 in the general elections of 1996 and 2001 and from
Dhaka-9 in the by-election of 1991 in the seat of
Begum Khaleda Zia. He lost the election in December 2008. He was elected to parliament in a by-election from
Bogra-6 on 3 April 2009. Bogra-6 was vacated, along with
Bogra-7, by former prime minister Khaleda Zia. From 28 October 2001 to 25 January 2009, Sircar served as the
Speaker of the Jatiya Sangsad. On 21 June 2002, he became acting president because of the resignation of
A. Q. M. Badruddoza Chowdhury. He remained acting president until a new president was elected on 6 September 2002. As speaker, he refused to allow discussion on the 2004 Dhaka grenade attack in parliament. He faced criticism for being partisan in allocating seats in the parliament. In 2008, his defence of the Bangladesh Nationalist Party and call for its return to power drew criticism.
The Daily Star wrote that the speaker should be above the political fray. On 13 April 2009, an Awami League-led parliamentary probe body reported that Sircar took 2.7 million taka unlawfully as medical bill without the permission of Prime Minister
Khaleda Zia during his tenure as speaker of the parliament. On 8 November 2012, the Anti-Corruption Commission filed charges against him, alleging he misappropriated 3.3 million taka. Sircar moved the High Court Division of the Supreme Court of Bangladesh, and the proceedings were stayed. Thereafter, the Appellate Division passed an order to dispose of Sircar's judicial review applications before the High Court Division. In March 2023, he deposited Tk 2.8 million (27.86 lakh) to the state exchequer following a court judgment in the graft case. In 2018, Sircar worked as the defense lawyer of former Prime Minister Khaleda Zia in the
Zia Orphanage Trust corruption case. ==Personal life==