Western Australian Senator Dorinda Cox has defected from the Greens to join the Australian Labor Party in what’s being seen as a stunning political shake-up.

Senator Cox made the announcement while standing alongside Prime Minister Anthony Albanese at a press conference in Perth on Monday afternoon.

“I am very, very grateful for this opportunity and I want to thank the Labor team for welcoming me,” Cox said, appearing visibly emotional as she confirmed her move to the government benches.

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The defection comes just weeks after the federal election and marks a significant blow to the Greens, reducing their Senate representation to 10 members.

Senator Cox, whose current term runs until 2028, was not up for re-election last month.

“Well, I think it’s been over a period of time that I’ve considered this. It hasn’t, as I said, been a decision that I’ve made lightly,” Cox explained.

Senator Dorinda Cox has defected from the Greens to Labor, of which she was formerly a member. (Richard Wainwright/AAP PHOTOS) Credit: AAP

She revealed that she informed new Greens leader Larissa Waters only 90 minutes before making the news public.

Prime Minister Albanese praised Cox’s decision, emphasizing that the approach came from the senator herself.

“She had come to a view that the difference that she wanted to make in the Senate and as a West Australian, were better served by being a member of the Labor Party,” he said.

“Senator Cox didn’t ask for anything, just asked for this to be considered.”

Albanese added that the Labor Party’s National Executive Committee met on Sunday afternoon and had approved her membership, with formal admission to the WA branch scheduled for Tuesday.

Cox, who was previously affiliated with the Labor Party before joining the Greens, said her decision was about effectiveness in government.

“What you can’t do from the crossbench is make change and being in the government and alongside the wonderful team that the Prime Minister has,” she said.

The political fallout was swift.

Within minutes of the press conference, Senator Cox’s profile was removed from the Greens’ official website, replaced with an “ACCESS DENIED” message on her former biography page.

Senator Cox informed new Greens leader Larissa Waters only 90 minutes before making the news public. Credit: Ross Swanborough/The West Australian

Her departure adds to the Greens’ post-election challenges.

While the party maintained a steady primary vote nationwide, it suffered significant losses in the lower house — largely due to the flow of preferences — including the defeat of former leader Adam Bandt in Melbourne and housing spokesperson Max Chandler-Mather in Griffith.

The party now holds just one lower house seat — Ryan, represented by Elizabeth Watson-Brown.

Senator Cox’s defection will reshape the political landscape in the Senate and strengthen Labor’s hand in Western Australia, while leaving the Greens to rebuild under new leadership amid dwindling parliamentary numbers.