New figures show there is a wide variation in the way police forces in England and Wales record allegations of rape.
The statistics show the proportion of rapes being classified as "no crime" vary from 2.4% in Gloucestershire to 30% in Kent.
The average figure for the 12 months leading up to March was 11.7% - falling from 15.5% four years ago - according to the data supplied by the Association of Chief Police Officers (ACPO) to BBC News under the Freedom of Information Act.
A spokesman for Kent Police said the rise in the percentage of "no crime" rapes followed a review into open cases.
He said: "Between January and March 2011 a team of specialist officers, alongside public protection detectives, undertook a review of all open reports of rape.
"As a result of this review, detailed inquiries carried out by officers resulted in some reports of rape being categorised as a "no crime". This resulted in above average "no crimes" for the period April 2010 - March 2011."
Surrey Police, whose "no crime" figure was 25.7%, said it had a "positive recording policy" and operated in accordance with Home Office rules.
A spokesman said: "Surrey Police treats all allegations of rape seriously and operates a positive recording policy meaning that the force records all allegations of rape, and incidents that may have amounted to rape, as rape offences in the first instance.
"In accordance with the Home Office counting rules we may "no crime" these records if, and only if, there is additional verifiable information to satisfy the force crime registrar that there is no substantive rape."
The figures come four years after an in-depth review of the way rape allegations are handled by police and prosecutors found some cases were being dropped prematurely.
The findings by Her Majesty's Inspectorate of Constabulary and Her Majesty's Crown Prosecution Service Inspectorate found that police wrongly recorded rape allegations as "no crime" in nearly a third of cases when the claims should have been investigated further.
Meanwhile the latest statistics also show disparities in "sanction detections", which is the proportion of cases where a suspect has been charged or cautioned.
Figures for Lincolnshire Police are just 11.1%, while Durham reached over five times this number with 60.8%.
Detective Inspector Sean Baxter of Lincolnshire Police said the force has recently introduced a dedicated investigation team to work on rape.
He said: "The Emerald Team is made up of experienced handpicked detectives and specially trained officers concerned solely with the investigation of rape offences from the cradle to the grave.
"We expect a significant impact as a result of this new team that is working closely with the Crown prosecution team to enhance the investigation and prosecution of offenders in these emotive crimes.
"The detection figures for rape April 2011 to the end of August 2011 are currently running at 16%."
ACPO lead for rape and serious sexual offences, Chief Constable Dave Whatton, said: "One of the most difficult offences police and prosecutors deal with is rape. Not only are the investigations complex, but understanding the true nature and extent of rape is difficult, because academic research shows that the incidence of this offence is underreported.
"Figures and statistics without context can never give the whole picture on how we manage and investigate rape across the criminal justice system."
Last year's landmark review into rape by Baroness Stern described the claim that only 6% of rapes lead to a conviction as misleading because it is based on all complaints to police, not all of which are brought to court. Almost 60% of those charged with rape are convicted, her report found.