Sally Talbot has resigned from State Shadow Cabinet.
The Upper House member held responsibilities for Disability Services, Mental Health and Child Protection.
Doctor Talbot says she wants to focus on building support for Labor in WA's south west in the wake of two election losses this year.
"We've had a state election and a federal election, and at both those elections, Labor lost," she said.
"That's the fact. We lost because we're not reflecting the values of the community, we lost because people don't feel that they can value what Labor offers to them, they don't trust Labor to give them a better future.
"I personally believe that that's wrong, I believe that Labor does offer working people and disadvantaged people a better future.
"And my personal judgement is that I can do more work to rebuild that community connection from the backbench than I can from the frontbench."
The Labor Leader Mark McGowan would not say who would replace Sally Talbot in Shadow Cabinet.