More than 500 black and ethnic minority individuals have died in suspicious circumstances while in state detention over the past 24 years, but not a single official has been successfully prosecuted, a report examining institutional racism has revealed.

The report, by the Institute of Race Relations, concludes that too little has changed to prevent black and Asian people dying in detention and that seemingly racist attitudes remain a concern, with a “large proportion of these deaths involving undue force and many more a culpable lack of care”.

It concludes: “Despite narrative verdicts warning of dangerous procedures and the proliferation of guidelines, lessons are not being learnt: people die in similar ways year on year.”

If anything, it says, the situation is worsening, with the privatisation and subcontracting of custodial services making it harder to call agencies to account. Almost 1,000 people have died in police custody alone since 1990. The report says that some of the deaths in prison revealed a “lack of care and disregard for human life that is so blatant that it often appears as deliberate acts and omissions by individuals and institutions”.

Harmit Athwal, co-editor of the report, which is to be unveiled in the House of Lords on Monday, said that while the official report into the murder of Stephen Lawrence in 1993 was intended to challenge racism within Scotland Yard, the ongoing catalogue of deaths suggested bigotry remained.

“‘If the Macpherson report was intended as a way of restoring community faith in the British police, the issue of deaths in custody is the one which is constantly undermining it. As more deaths take place and no one is ever prosecuted, it inevitably sows seeds of incredulity, anger and despair,” said Athwal.

The majority of the 509 black and ninority deaths studied since 1991 – 348 – occurred in prison, with 137 cases in police custody and 24 deaths recorded in immigration detention.