The riding of Laurier-Dorion was created for the 1994 election, in which Sirros defeated PQ candidate Benoît Henry by 6,930 votes.
He was most notably the Minister of Indian affairs under Robert Bourassa and Minister of Natural Resources under Daniel Johnson, Jr.
He was the National Assembly's First Vice-President from June 2003 to June 2004.
Sirros left his seat in June 2004; he was then appointed Quebec Delegate General for Belgium, and served in the position until 2013.
In December 2014, he was appointed the Quebec Delegate General for the United Kingdom.