Hundreds of current and former detainees of Western Australia’s only youth detention centre have filed a class-action lawsuit against the state government.

The case, filed by Sydney-based lawyer Stewart Levitt, includes testimony from around 600 people who claim they were mistreated at Banksia Hill Youth Detention Centre or its predecessor facility, Rangeview.

The facility has been the centre of criticism for its treatment of detained children, earning rebukes from WA’s Children’s Court President Hylton Quail on multiple occasions and also becoming the subject of an ABC Four Corner’s episode last month exposing the use of a dangerous restraint technique.

Mr Levitt said claimants range in age from current detainees to adults who had served time in the youth detention system as far back as 1997.

He said claimants, who are mostly Indigenous, are seeking financial redress and believes the case it potentially worth hundreds of millions of dollars due to the high number of people involved.