The nation's highest court on Wednesday ruled the Federal Court is able to hear legal claims challenging the adequacy of healthcare in detention.

More than 50 cases relating to allegations the Australian government failed to provide adequate healthcare were on hold in the Federal Court pending the judgment.

Maurice Blackburn principal lawyer Jennifer Kanis said the decision provides a clear pathway for current and future legal claims.

"The High Court has confirmed people in offshore detention in Nauru and Manus Island can seek urgent, lifesaving treatment through the Federal Court," she said in a statement.

"This decision means that refugees and asylum seekers will not have to endure the additional cost, inconvenience and delay of bringing healthcare claims through the High Court.

"This is an important precedent regarding where asylum seekers' claims challenging the adequacy of healthcare should be heard."

The federal government brought forward the legal challenge and argued the Migration Act required claims to be heard only by the High Court.

The court looked at four test cases of children in offshore detention, two represented by Maurice Blackburn and two by not-for-profit legal firm the National Justice Project.

One of the cases involved a girl at Nauru who at the age of two was diagnosed with a life-threatening neurological condition.

Doctors recommended she be medically evacuated to Australia for urgent tests including a brain scan.

She was sent to Papua New Guinea for treatment.

A court later ordered her urgent transfer to Australia for recommended tests and ongoing medical care.

"We've argued successfully at every stage that the Federal Court has the jurisdiction to hear these claims," National Justice Project director George Newhouse said.

"This decision vindicates the right of our clients to seek justice for the cruel and inhumane treatment that they suffered."

Australian Associated Press