Some UK police forces fail to record more than four in 10 rape claims on official crime records, it was reported today.
Figures obtained by the BBC, using Freedom of Information legislation, found wide regional variations.
In Northumbria, 172 of a total 382 reports of rape (45 per cent) did not make it into official Home Office figures.
The BBC said rules state only allegations verified as false, reported to the wrong force or recorded in error can be removed.
Police in Durham said only five of 130 cases had been "no-crimed", yet the BBC said figures showed a further 83 cases were never officially recorded in the first place.
Forces in Humberside, Gloucestershire, and Northamptonshire recorded at least 90 per cent of cases for investigation.
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 had been made into investigating rapes, but admitted there was still much more to do.