WA Senator and Yamatji-Noongar woman Dorinda Cox has renewed her call for state, territory and federal governments to implement in full all 339 recommendations from the Royal Commission into Aboriginal Deaths in Custody, and relevant international conventions, in the wake of two Indigenous deaths in custody in just four days in her home state.

On Tuesday a First Nations man collapsed and died at Greenough Regional Prison, following the death of a First Nations woman at Wandoo Rehabilitation Prison on Christmas Eve after a "medical event" on December 21.

Senator Cox noted that of the more than 100 people to die in custody in Australia this year, over one in four were Indigenous.

"First Nations communities across WA are in distress over yet another death in custody," she said.

"The final months of 2022 have brought so much grief and sorrow to families who've lost loved ones so tragically.

"We cannot continue to accept First Nations deaths in custody as unavoidable. We need to ensure that everyone in custodial care receives adequate health and mental health care, and access to support services including visits by the community when needed."

Senator Cox said Commonwealth and state governments have had "the solutions to change these dire outcomes… for over thirty years".

"I call on state governments to implement all of the recommendations of the Royal Commission into Aboriginal Deaths in Custody report handed down in 1991, and the Commonwealth to urgently fund and implement the United Nation's Optional Protocol to the Convention Against Torture and Other Cruel, Inhuman or Degrading Treatment or Punishment (OPCAT) which was ratified in 2017," she said.

"We cannot keep turning a blind eye and accepting these devastating outcomes for First Nations people and their families."

Senator Cox was backed by her Greens colleague, state MLC Brad Pettitt, who noted WA's high incarceration rate.

"These two tragic deaths in custody in short succession around Christmas time are undoubtedly devastating for the families of these relatively young people," said Dr Pettitt.

"WA continues to have the highest rate of incarceration in the nation and it is time that earnest steps were taken to implement the recommendations of the Royal Commission and to do more to ensure these tragedies are not repeated."