Days after voting against it to support a resolution on Palestinian statehood, Senator Fatima Payman resigned from the Labor Party, which is in power in Australia.
Labor imposes severe sanctions on anyone who compromise its policy stances, and Ms. Payman was already "indefinitely suspended" from the party caucus for her repeated threats to do so.
“This is a matter I cannot compromise on,” the 29-year-old said on Thursday, adding that she was “deeply torn” over the decision.
Prime Minister Anthony Albanese said Ms Payman had thanked him for his leadership and denied allegations she had been intimidated into quitting.
Ms Payman will now join the crossbench as an independent senator.
The 29-year-old Muslim lawmaker, whose family fled Afghanistan after it fell to the Taliban in 1996, is Australia’s first and only hijab-wearing federal politician.
“Unlike my colleagues, I know how it feels to be on the receiving end of injustice. My family did not flee a war-torn country to come here as refugees for me to remain silent when I see atrocities inflicted on innocent people,” she said during a press conference on her resignation.
The conflict in Gaza has become a volatile political issue in Australia that all sides have sought to carefully manage.
Officially the government favours a two-state solution, but it did not back the motion on statehood after trying - and failing - to insert a condition that any recognition should be “as part of a peace process”.
The Israeli military launched a campaign to destroy the Hamas group which runs Gaza in response to an unprecedented Hamas-led attack on southern Israel on 7 October, during which about 1,200 people were killed, and 251 others were taken hostage.
More than 37,900 people have been killed in Gaza since then, including 28 over the past 24 hours, according to the territory's Hamas-run health ministry.
Ms Payman said that since crossing the Senate floor to vote with the Greens party last Tuesday she had received “immense support” from some colleagues, and “pressure… to toe the party line” from others. She also reported receiving "death threats and emails that were quite confronting" from members of the public.
Prime Minister Anthony Albanese, who handed down the indefinite suspension on Sunday, had repeatedly said Ms Payman could rejoin the caucus – where MPs discuss the government’s agenda - if she was willing to participate “as a team player”.
But in a statement earlier this week, Ms Payman said she had been “exiled” by Labor - explaining that she had been removed from meetings, group chats and all committees.