Released by Human Rights First, a group of US lawyers, the report claims as many as 98 detainees have died in custody, 34 of those confirmed homicides as defined by the US military.
The group allege that 11 more deaths were deemed suspicious and that between eight and 12 people were tortured to death. The dossier claims charges over the deaths are rare and sentences were light.
“Looking closely at these cases, we found time and again badly flawed investigations, and a lack of command responsibility for what’s gone wrong – especially in cases where victims were tortured to death,” Deborah Pearlstein, Director of the US Law and Security Program at Human Rights First said in a press statement.
“The result across the board has been to create a culture of impunity, where no one, especially not command, is held fully accountable for detainee deaths,” she said.
“If the United States is serious about preventing torture going forward, there must be accountability up and down the chain of command,” Ms Pearlstein said.
The report comes a week after SBS' Dateline program aired previously unseen pictures showing apparent US abuse of prisoners at Iraq's Abu Ghraib jail in 2003.
Key findings
Among the key findings of the report was a failure by Commanders to report detainee deaths in custody within their command, Commanders reporting deaths days and sometimes weeks after the event and in other cases actively interfering in investigation efforts.
Investigators are also implicated as having failed to interview thoroughly and effective punishment was often “too little and too late.”
The 82-page document speaks of one case were a detainee was made to jump off a bridge and another where a prisoner was forced into a sleeping bag, wrapped with electrical cord and suffocated to death.
The report urges the US Government to take a zero tolerance policy for commanders who fail to take the issue of deaths in custody seriously.
Response
Details of the report were first aired on BBC television’s Newsnight program on Tuesday, where the US Pentagon said it was unaware of the dossier.
"We haven't seen the report yet. Where we find allegations of maltreatment we take them very seriously and prosecute," the Pentagon told the BBC.
US ambassador to Iraq, Zalmay Khalilzad, told Newsnight that the US always investigates allegations of abuse in custody and dispenses appropriate punishment if illegal actions have taken place.
"If those reports are true, of course they would be terrible abuses and they would be illegal things. Those who are responsible for them would be investigated and they will be punished," he said.
Former White House legal adviser, David Rivkin, told AFP that the numbers had to be put in perspective.
"[If] 10 people were tortured to death out of over 100,000 detainees in Iraq and Afghanistan" that was "a better rate" than in both world wars and "most civilian penal systems," he said.
"It is not a scandal. Bad things happen in detention. A lot of them died for reasons that have nothing to do with it," said Mr Rivkin.
But Amnesty International UK demanded an investigation into the deaths. "We want to see the US and its allies allowing a full independent and impartial investigation into these deaths, as well as mounting incidents of alleged torture and other mistreatment,” a spokesman for the human rights group said.