She was a Labor Party member of the Legislative Assembly of Queensland from 1997 to 2009, representing the district of Kurwongbah.
[1] Lavarch was first elected to the seat of Kurwongbah, situated in Brisbane's northern suburbs, in a by-election on 24 May 1997.
On 28 July 2005, Lavarch was appointed Queensland's Attorney-General and Minister for Justice—the first woman to hold a substantive role as Attorney-General in Queensland (Joan Sheldon had held the role in an interim capacity for seven days in 1996).
[1] On 27 April 2016, Lavarch was announced as the Labor candidate for the federal seat of Dickson at the 2016 election, eventually losing to Immigration Minister, Peter Dutton.
Lavarch sought ALP preselection to run in Dickson again in the 2019 election but was defeated by Ali France, the daughter of her former parliamentary colleague Peter Lawlor.