Ambareesh was elected to the 12th Lok Sabha from Mandya Parliamentary Constituency as member of the Janata Dal. He later joined the Indian National Congress and has since continued to represent the same Mandya Lok Sabha constituency for two more terms. He was minister of state for Information and Broadcasting in the 14th Lok Sabha, but resigned over his dissatisfaction with the Cauvery Dispute Tribunal award, though the resignation was not formally accepted. He was defeated in the May 2009 General Elections.
During the course of his public life, he has held the following positions:
Member, 12th Lok Sabha: 1998-1999
Member, 13th Lok Sabha: 1999-2004
Member, 14th Lok Sabha: 2004-2009
Minister of State, in the Ministry of Information and Broadcasting, from 24 October 2006 to 2008.
Resigned as the Minister of state in the Ministry of Information and Broadcasting, protesting against the injustice done to Karnataka by Kaveri dispute tribunal in 2008.