South Yorkshire Police Force allegedly told a Rotherham mother that investigating 125 potential sex abusers whose names were found on her daughter's mobile phone would "breach her human rights".
The claims were made by Professor Alexis Jay, author of this week's damning report into how police and social services failed to protect 1,400 children abused by gangs of Asian men in the South Yorkshire town.
The girl's phone allegedly contained descriptions of the abuse the girl had suffered at the hands of the men, said Professor Jay.
She also claimed that she received allegations that police told a 12-year-old, who was forced to have sex with five men, she was not abused as police officers said the sex was "consensual".
The report investigates how the abuse was not investigated for 16 years, between 1997 and 20013, because authorities feared being accused of racism.
In the interview Professor Jay, who had investigated complicated cases of child sexual exploitation before, describes her shock as the scale of the abuse in Rotherham became clear.
"The utter brutality is what shocked me most," she says. "It is really hard to describe it – the horrible nature of the sexual acts and the brutality of the controls these girls were subjected to. There was a vast amount of truly horrific material. I was taken aback at how callous, how violent, the operations were. These were girls of 11 and 12.
"They were children. The violence was worst. Petrol dousing was used as a form of intimidation. Oral and anal sex were so often a means of control and punishment. It was truly frightening that people in our country could be doing that."
She condemns repeated police failures to investigate the incidents.
"Oh, it was quite shocking how callous the police were in the early years, the attitudes about 'consent', the inaction around missing people. Parents just gave up on the police. They wondered: what's the point? Some wrote letters to politicians and councillors in desperation: 'Please stop this,' 'How can I get help?' There were a lot of good procedures, but no one checked if they were working."
Yesterday, South Yorkshire's chief constable, David Cromley, reacted to the report, and vowed to "fully investigate" the abuse.
He said: "The report into CSE (child sexual exploitation) in Rotherham laid bare the failings of South Yorkshire Police over a number of years."