Leicestershire Police have failed to record over 21,000 alleged crimes, according to a new report.
An assessment by HM Inspectorate of Constabulary and Fire & Rescue Services (HMICFRS) said the force needed "vast improvement".
HM Inspector of Constabulary Zoe Billingham said: "We estimate that the force fails to record 21,200 reported crimes each year, including reports from victims of crimes of a sexual nature, and of violence."
Leicestershire Police said it noted the report and the inspectorate's conclusions "which are consistent with half of the forces it has inspected to date."
They acknowledge that there are areas that they need to improve upon, and say they "are taking steps to address these administrative shortfalls."