▁official ▁opposition . ▁The ▁leader ▁of ▁the ▁largest ▁party ▁in ▁opposition ▁becomes ▁the ▁Le ader ▁of ▁the ▁O pp osition . ▁The ▁opposition ▁plays ▁a ▁central ▁role ▁in ▁deb ating ▁government ▁ideas ▁as ▁well ▁as ▁scr ut in ising ▁the ▁government ' s ▁business ▁and ▁its ▁ag enda . ▁However , ▁the ▁opposition ' s ▁power ▁is ▁limited ▁while ▁the ▁government ▁commands ▁a ▁majority ▁in ▁the ▁Legisl ative ▁Assembly ▁due ▁to ▁the ▁tradition ally ▁strong ▁party ▁discipline ▁throughout ▁Australia . ▁Part ies ▁must ▁have ▁at ▁least ▁ 5 0 0 ▁members ▁on ▁the ▁Victor ian ▁elect oral ▁roll , ▁have ▁a ▁party ▁constitution ▁and ▁register ▁with ▁the ▁Victor ian ▁Elect oral ▁Commission ▁to ▁receive ▁official ▁status . ▁ ▁The ▁Labor ▁Party ▁has ▁been ▁in ▁Government ▁since ▁ 4 ▁December ▁ 2 0 1 4 , ▁led ▁by ▁the ▁Premier ▁and ▁leader ▁of ▁the ▁Labor ▁Party ▁in ▁Victoria , ▁Daniel ▁Andrew s . ▁ ▁The ▁Le ader ▁of ▁the ▁O pp osition ▁Co al ition ▁is ▁Michael ▁O ' B rien , ▁who ▁was ▁elected ▁as ▁the ▁leader ▁of ▁the ▁Liberal ▁Party ▁on ▁ 6 ▁December ▁ 2 0 1 8 ▁after ▁their ▁election ▁defeat , ▁replacing ▁former ▁leader ▁Matthew ▁Guy . ▁The ▁Gre ens ▁are ▁led ▁by ▁Sam anth a ▁Rat nam . ▁ ▁Parliament ary ▁so vere ig nt y ▁Parliament ary ▁so vere ig nt y ▁within ▁Australia ▁is ▁a ▁complex ▁matter ▁due ▁to ▁the ▁nature ▁of ▁the ▁mon archy , ▁feder ation , ▁and ▁the ▁grad ual ▁central isation ▁of