The family of a 22-year-old Aboriginal woman who died in police custody in Western Australia says they are prepared for a public and lengthy battle to bring those responsible to account.

Community groups, lawyers and politicians have formed an alliance in support of the family's calls for justice. The chairman of the Deaths in Custody Watch Committee of Western Australia, Marc Newhouse, said the family had been devastated by the tragic circumstances of the death, but would begin a public campaign next week to put pressure on the WA government for a public inquiry into the death.

The Yamatji woman known as Ms Dhu (cultural reasons prevent the publication of her full name), was taken into custody at South Hedland watch house on August 2 for unpaid fines.

She was taken to hospital twice in two days after vomiting and complaining of severe pain, but was cleared both times to remain in custody. She died at Port Hedland hospital on August 4, after reportedly begging police for medical attention.

Ms Dhu's death had "struck a chord", Mr Newhouse said.

"There's widespread community concern about this death in custody, particularly given her age and the circumstances," he said. "It's raised alarm bells across the country."

The chief executive of the Aboriginal Legal Service WA, Dennis Eggington, said deaths in similar circumstances would continue unless the state addressed an appalling record of locking up Aboriginal people.

"It horrifies me to think that people are still going into custody and are ending up passing away because of a medical condition," Mr Eggington said.

"Why wasn't the young lady given the medical attention she obviously needed?"

He said the ALS was also demanding authorities provide more information about the nature of Ms Dhu's unpaid fines, which reportedly totalled no more than $1000. In WA, people jailed for unpaid fines can reduce their debt by $250 for each day in jail.

"The recommendations [of the Royal Commission into Aboriginal Deaths in Custody] also said in cases like this that jail should be a last resort," Mr Eggington said. "Jail, in this instance, was a first resort and that's not acceptable."