Within the federal government, Mirabella sat in the backbench until 2007. During this time, in 2005, she attracted public attention as a key member of an informal "ginger group" of Liberal backbenchers. She chaired this group with Victorian Senator Mitch Fifield. The group argued for "tax reform" (in essence, tax cuts paid for by reductions in government spending), sparking public debate on the topic. Although Fifield stepped away from the group after budget cuts in 2005, Mirabella continued for a time as the group's chair. While on the backbench, Mirabella took a strong stance on the prominent issue of asylum seekers, criticising a group of four fellow Liberal backbenchers, including Petro Georgiou and Judi Moylan, for opposing government policy on mandatory detention. In August 2005, she called for Muslim women to be required to remove their head dress when posing for photo identification."Bishop backs headscarf ban". The Age 28 August 2005. Retrieved 24 August 2012. Mirabella was an advocate of voluntary student unionism (VSU) and strongly supported the legislation proposed by Brendan Nelson.Woe, David (10 August 2005). "Student unionism divides Coalition". The Age Retrieved 24 August 2012.
