He was a close aide to Benazir Bhutto who had appointed him the party's deputy secretary general in 1997 and leader of the opposition in the Senate in 2005.

[1][5] He was inducted into the federal cabinet in 1994 and appointed as the Minister of State for Law and Justice[3] during the second government of Benazir Bhutto[6] where he served until 1996.

[3][5] After the victory of PPP in 2008 Pakistani general elections, he refused to join the federal cabinet of Yousaf Raza Gillani due to reluctance to take oath from then president of Pakistan Pervez Musharraf.

[5] After resignation of then President Pervez Musharraf, On 3 November 2008, Rabbani was inducted into the federal cabinet with the rank of federal minister[3][6][10] and appointed as Advisor to the Prime Minister on Inter-Provincial Coordination where he served until 9 March 2009 when he resigned[1][11] against the decision of PPP to nominate Farooq Naek as chairman of the Senate.

[18] Despite his recommendations, none of the provisions in the packages would be carried out by Prime Minister Yousaf Raza Gillani who would later entangle with the Supreme Court over the missing persons scandal.

As far as the U.S. is concerned, the message that has gone with this resolution will definitely ring alarm bells, vis-à-vis their policy of bulldozing Pakistan.

"[21] In April 2011, Rabbani also heavily criticised the US over their drone operations in North-Western Pakistan in the Parliament, commenting that United States is following a major violation of international law and human rights.

In 2003, he authored a book, "LFO: a fraud on the Constitution", in a direct opposition to President Pervez Musharraf and a scheme of legitimising his rule.

"[25] His statement came during the 2013 general elections, in which, left-wing parties were under immense pressure from the right-wing insurgent groups to limit their political campaigns.

[25] While accusing former president Parvez Musharraf for supporting the ultra-conservative alliance to curb the left-wing parties, Rabbani, with another Marxist Taj Haider, accused the West and the United States of supporting right wing parties for their bid in the elections.