Three-quarters of survivors of sexual violence who took part in a survey say their mental health worsened because of how the police investigated.
Some said the perpetrator continued to harm them because police did not take their report seriously; others wished they had never contacted the police.
Four in 10 respondents did not feel believed, according to the research.
Safeguarding minister Sarah Dines said she would be encouraging chief constables to reflect on the findings.
One survivor said: “I am more afraid of the police than being raped again.”
Another said: “I would rather be assaulted 1,000 times over than go through the police process again.”
Some 1,968 survivors who had interacted with the police opted to take part in the anonymous survey between 16 January and 30 June. A further 190 survivors shared why they chose not to make a police report.
It was funded by the Home Office as part of Operation Soteria Bluestone. All police forces in England and Wales are signed up to the programme, aimed at transforming how rape and sexual offences are investigated.
Some survivors told the survey that officers had protected them from further harm, “treating them with tremendous kindness, empathy, and care”.
These were, “sadly”, a minority, the report said.
Almost a third (31%) said they did not always feel safe in the presence of the officers.
In addition to 75% saying their mental health deteriorated, 55% said their physical health decreased, 41% said their personal safety declined, and 54% said their trust in police declined due to their police experience.
One participant said seeing a police car now triggers a panic attack.
More than half (56%) of respondents said they were unlikely to report a rape to the police again.
Some said they had been raped again since their report, but had not told the police. They said they feared the police more than the perpetrator.
The report says this “suggests that as a result of traumatic police experiences, some survivors have de-facto lost access to what should be a universal public service available to all – being able to call the police when in danger”.
Professor Katrin Hohl, lead academic on the survey, said: “The findings are sobering. They evidence the tremendous harm poor policing has caused to many rape and sexual assault survivors.”
Black and minority ethnic survivors were less likely than white respondents to feel the police had looked at all the evidence, made them feel comfortable, or made them feel like the rape or sexual assault was not their fault.
People who had been harmed by a current partner reported the poorest experiences, compared with those assaulted by a stranger or those with other relationships to the perpetrator.
Autistic survivors and those with a physical disability also reported poorer experiences.
But people who either reported the case in the previous six months or who had contact with the police in the three months prior reported significantly better experiences.
Six in 10 of these respondents said police did a good job in their case, compared with 36% whose last police contact was more than three months ago.
This could be an early sign of improvements in how cases are being handled, the report says. It could also, however, reflect that experiences tend to be more positive in the initial stages of the investigation.
Researchers said the survey is not representative of all survivors’ experiences with the police, due to the way participants were selected, and therefore cannot be used to generalise.
Of those who took part, 27 said the person they had accused was a serving police officer at the time of the assault. Three people were allowed to join a police force despite the rape or sexual assault report made against them.
One survivor said the officer investigating their case went on to rape them.
Safeguarding minister Sarah Dines said: “Rape is an abhorrent crime and I have been clear that we need radical improvement in the way the police handle and investigate rape and sexual violence to ensure all victims have the best support possible throughout the entire process.
“I am committed to supporting officers to strengthen their response to these crimes, which is why I am continuing to fund the ambitious programme, Operation Soteria, to transform the way that rape investigations and prosecutions are handled and progressed, with a focus on investigating the suspect rather than the victim.”
The National Police Chiefs Council (NPCC) said Operation Soteria would improve victims’ experiences and address low charge and conviction rates.
Thanking survivors for taking part in the survey, Chief Constable Sarah Crew, NPCC lead for rape and adult sexual offences, said: “We have taken an honest and open look at the way we work, have welcomed academics in to scrutinise it and provide us with direction for how we can improve.
“This is not easy, but it is vital, we are determined to do better for victims.”
The survey will remain open until June 2024.