A Same-Sex Marriage Bill set to be debated in State Parliament could be the first gay-marriage bill in Australia to pass a Federal Government challenge, according to its author, WA Greens MLA Lynn MacLaren.

The ACT Legislative Assembly passed its Marriage Equality Bill in October 2013 but the change was short-lived, with the Commonwealth immediately challenging it in the High Court.

Greens MLA Lynn MacLaren says her gay-marriage bill is poised to withstand a High Court challenge. Credit:AP

While Australia's first same-sex marriages took place in Canberra on December 4 they were annulled when the High Court ruled the ACT's laws were inconsistent with the Federal Marriage Act and therefore unconstitutional.

The ACT is the only state or territory to pass a gay marriage bill, with a Tasmanian Marriage Equality bill passing through the lower house of Tasmanian Parliament before being defeated in the upper house in 2012.