Police in Lancashire fail to record one in 15 reports of rape.
The victims' commissioner for England and Wales called the systemic under-reporting of rape "shocking and unforgivable" and said officers should explain why they are letting victims down.
Independent audits of 36 police forces found that one in 10 rape reports analysed were recorded incorrectly.
Studying nearly 3,700 cases, Her Majesty's Inspectorate of Constabulary and Fire and Rescue Services unearthed errors ranging from incorrect paperwork to reports missing from official records.
Lancashire Constabulary's latest audit, published in 2019, revealed eight out of 114 audited rape reports (seven per cent) were not recorded properly.
Victim's commissioner Dame Vera Baird said there is "no excuse" for errors, which mean investigations are not carried out and perpetrators escape justice.
"It takes enormous courage to come forward and report a sexual crime," she added.
"Victims would be devastated to learn that it has not been properly recorded – they deserve better wherever they live.
"It would be interesting to hear why forces who are recording poorly explain themselves."
Overall, Lancashire Constabulary was found to have recorded seven per cent of crimes reported to it incorrectly.
Of the 1,093 cases analysed, 349 were linked to domestic abuse.
But auditors noted 41 of these did not appear in official figures, including 36 violent offences.
HMICFRS found the force to be "of concern" for crime-reporting.
Poor police record-keeping sent criminals a signal that they were free to reoffend, warned Dame Vera.
"We must remember a crime is not merely a statistic – it can have a devastating impact upon the lives of its victims," she added.
"When those victims report the crime to the local police, the very least they are entitled to expect is that it will be accurately recorded.
"Failure to do so can only undermine public confidence in the police and the wider criminal justice system."
A National Police Chiefs' Council spokesman said: "The rate of crime reporting to police forces has increased in recent years, and we are working to further improve the accuracy of crime recording, which is governed by detailed counting rules set out by the Home Office.
"Forces receive regular audits from HMICFRS and work hard to meet objectives within their specific action plans through the use of in-force scrutiny panels, independent oversight, and with the help of crime incident registrars who can assist officers with the appropriate classification and recording requirements."
Officers always encourage victims to report crimes, he added.