Rotherham's MP Sarah Champion has said she finds it "difficult to believe" that a police officer mentioned in a report into the treatment of a sex abuse survivor cannot be identified.
Ms Champion said South Yorkshire Police needed to make "dramatic changes" in the wake of the police watchdog report.
It said police failed to protect the complainant, exposing her to abuse.
It also found an officer - whose identity is a mystery - said "racial tensions" meant nothing could be done.
The Independent Office for Police Conduct (IOPC) looked at several complaints made by a Rotherham woman, who was abused as a child for several years.
In its report, initially leaked to the Times newspaper, the watchdog upheld the woman's complaints, saying that "police took insufficient action to protect you from harm" and that "police failed to adequately deal with offenders".
The IOPC also upheld a complaint that the victim's father was told by a senior - but unidentifiable - officer that the force was aware abuse "had been going on 30 years and the police could do nothing because of racial tensions".
South Yorkshire Police said on Saturday it accepted the findings of the IOPC.
A report in 2014 by Prof Alexis Jay found at least 1,400 children were subjected to sexual abuse in Rotherham between 1997 and 2013, predominantly by men of Pakistani heritage.
Ms Champion told BBC Radio 5 live that the IOPC inquiry was the latest in a series of investigations that showed "victims and survivors were let down by paid professionals".
"Apparently now South Yorkshire Police don't actually know who the officers were that repeatedly let down this survivor, which I find incredibly difficult to believe," the MP said.
"I think what we as a town need to see, and definitely for the survivors to get closure, they need to see cases of misconduct. They need to see people held to account."
South Yorkshire Police could not be contacted for comment about the Labour MP's remarks.
Her views were echoed by Sammy Woodhouse, who was abused as a teenager in the South Yorkshire town.
She said she was not shocked by the report's findings.
"I think for the last six years we've more than proved what happened to us," said Ms Woodhouse.
"How we were viewed how we were treated, failed, ignored, blamed... unfortunately that's not a thing of the past, it's still happening today.
"We've started to now see perpetrators that have committed the rapes and the abuse being held to the account, but yet whenever when it comes to professionals I feel that we constantly hit a brick wall and I don't think anybody will be ever held to account."