Rape claims are being left off official crime records, the BBC has learned.
Figures obtained following a Freedom of Information request showed some UK police forces were failing to record more than 40% of cases.
Rules state only allegations verified as false, reported to the wrong force, or recorded in error can be removed.
The Association of Chief Police Officers said advances had been made in rape investigation but campaigners said women were being denied justice.
The figures showed wide regional variations but some forces had such a high number of cases removed from records - known as "no-criming" - that critics said it was evident the rules were not being properly applied.
Cause for concern
In Northumbria, there were 382 reports of rape. Of those, 172 never made it into official Home Office figures and that was before any were "no-crimed".
Police in Durham said only five of 130 cases had been "no-crimed" yet the figures showed a further 83 cases were never officially recorded in the first place.
In contrast, forces in Humberside, Gloucestershire, and Northamptonshire recorded at least 90% of cases for investigation.
HM Inspectorate of Constabulary demanded improvements in recording rape claims two years ago but has admitted there is still cause for concern.
The figures also showed hundreds of complaints lodged in the year to March 2008 never went forward to a full investigation.
The Association of Chief Police Officers (Acpo) said significant advances have recently been made into investigating rapes but admitted there was still much more to do.
Lisa Longstaff, of campaign group Women Against Rape, accused police of not taking rape seriously enough.
She said police have 72 hours in which to investigate a rape allegation and declare it a crime but some were using this as a way to avoid investigating.
Figures obtained following a Freedom of Information request showed some UK police forces were failing to record more than 40% of cases.
Rules state only allegations verified as false, reported to the wrong force, or recorded in error can be removed.
The Association of Chief Police Officers said advances had been made in rape investigation but campaigners said women were being denied justice.
The figures showed wide regional variations but some forces had such a high number of cases removed from records - known as "no-criming" - that critics said it was evident the rules were not being properly applied.
Cause for concern
In Northumbria, there were 382 reports of rape. Of those, 172 never made it into official Home Office figures and that was before any were "no-crimed".
Police in Durham said only five of 130 cases had been "no-crimed" yet the figures showed a further 83 cases were never officially recorded in the first place.
In contrast, forces in Humberside, Gloucestershire, and Northamptonshire recorded at least 90% of cases for investigation.
HM Inspectorate of Constabulary demanded improvements in recording rape claims two years ago but has admitted there is still cause for concern.
The figures also showed hundreds of complaints lodged in the year to March 2008 never went forward to a full investigation.
The Association of Chief Police Officers (Acpo) said significant advances have recently been made into investigating rapes but admitted there was still much more to do.
Lisa Longstaff, of campaign group Women Against Rape, accused police of not taking rape seriously enough.
She said police have 72 hours in which to investigate a rape allegation and declare it a crime but some were using this as a way to avoid investigating.
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