Northamptonshire Police wrongly cancelled crime records for one in 10 sexual offences and violent offences, analysis of an official audit shows.
The force also did not inform two out of 19 victims that the offence had been dropped, according to Her Majesty's Inspectorate of Constabulary and Fire and Rescue Services (HMICFRS).
But a study of the watchdog's inspections by the BBC Shared Data Unit, which this newspaper is part of, did find the county's police made no mistakes with rape or robbery reports.
A Northamptonshire Police spokeswoman said: “Providing victims of crime in Northamptonshire with the level of support they deserve is very important to us and since these figures were produced, we have made significant progress in this area.
“We value the views of HMICFRS and Northamptonshire Police work closely with them.
"We are not in a position to discuss individual cases but our overall grading demonstrates our victim-focused approach.”
The Shared Data Unit analysed the most recent inspectors' reports of crime records from 43 police forces across England and Wales.
The reports detail whether inspectors believed the correct decisions were taken to cancel crimes after reviewing a sample of reports.
Northamptonshire Police was deemed as 'requires improvements' in crime reporting accuracy and 'good' overall by the HMICFRS earlier this year.
Katie Russell, from Rape Crisis England & Wales, said: “This is part of a wider context in which our criminal justice system has been significantly failing victims and survivors of rape, sexual abuse and all forms of sexual violence for many years.
“The majority of people subjected to these crimes still don’t have the confidence to report to the police, but despite increasing numbers who are choosing to come forward, charging, prosecution and convictions rates are at an all-time low, while the overwhelming majority of rapists and sexual offenders are walking free.
“Especially considering the wide-ranging, significant and often lifelong impacts of sexual violence and abuse on victims and survivors, these criminal justice failings are completely unacceptable.
"People who have been through such considerable trauma simply need and deserve better."
Police forces in England and Wales can cancel or transfer a crime when one or more of five criteria are met.
- Transferred: when a crime is committed outside of the jurisdiction of the police force in which it was recorded and is then passed on to that force
- Cancelled: Additional verifiable information determines that no notifiable crime occurred, duplicate record or part of a crime already recorded, crime recorded in error, or self-defence claimed
A National Police Chiefs’ Council spokesman said: "Our priority is to ensure that victims have the confidence to report crimes, safe in the knowledge that they will be fully investigated and that they will receive appropriate support and information.
"We are working to further improve the accuracy of crime reporting, which is governed by detailed counting rules set out by the Home Office."