One of Britain's largest police forces is failing to record thousands of alleged offences including reports of rape, a highly critical report has found.
Inspectors warned victims could be at more risk of harm because of shortcomings at West Midlands Police.
An assessment by HM Inspectorate of Constabulary and Fire & Rescue Services (HMICFRS) found 83.8% of reported offences were recorded by the force.
This means West Midlands is not recording at least 38,800 reports of crime each year, the watchdog estimates.
The 16.2% of reported crimes that go unrecorded included sexual offences, domestic abuse and rape.
It highlighted the recording rate for violent crime, which was 77.9%, as a particular cause of concern, adding: "This means that on too many occasions, the force is failing victims of crime."
HM Inspector of Constabulary Wendy Williams said: "I am very disappointed with the result of our recent inspection into how West Midlands Police records crime.
"We estimate that the force fails to record over 38,800 crimes every year.
"This is not just low-level crime: it includes sexual offences and violent crime.
"Not only does this mean the force cannot fully understand the demand it faces to plan accordingly, but it also means that victims could potentially be at more risk of harm, without the required support."
She said the force needs to improve how it manages domestic abuse cases, saying the inspectorate found a large number of cases where safeguarding requirements for victims had not been considered or recorded, and for which no investigation had been carried out.
HMICFRS noted improvements in West Midlands Police's processes since 2014 but rated the force as inadequate for effectiveness at recording reported crime.
The findings are the latest issued under a series of rolling inspections looking at the crime data "integrity" of every police force in England and Wales.