Lincolnshire Police recorded third of rape reports as 'no crime'
A third of adult rapes reported to Lincolnshire Police in a year were recorded as "no crime", figures show.
This was the highest "no crime" rate for any force in England and Wales, in the 12 months to the end of March 2013.
Rape Crisis said it was "deeply concerned" by the data, believing it was unlikely so many reports of rape were false.
Lincolnshire Police said there was not a "culture of disbelief" and it investigates all reports thoroughly.
For child rape, the "no crime" rate was 5% in England and Wales, compared to 19% in Lincolnshire.
Det Supt Rick Hatton said: "We cannot entirely explain why the percentage of rape 'no crimes' in Lincolnshire is higher than in other areas but we are affected by the relatively low level of such crimes in Lincolnshire.
"This means that small variations in numbers can make large differences in percentage terms."
The Inspectorate of Constabulary has compiled data from across all 43 police forces in England and Wales.
Lincolnshire Police recorded 110 adult rapes in the 12 months to the end of March 2013, and subsequently decided 36 (33%) had not taken place.
In contrast, the average "no crime" rate for rapes in England and Wales was 12%, and the lowest was 3%, in Cumbria.
Katie Russell, from Rape Crisis, said: "It seems highly unlikely that of those that do get reported [in Lincolnshire] a third are not pursuable and no crime has taken place.
"Successive studies have shown that false reporting of rape is no higher than other types of crime, in fact, some studies suggest false reporting might be higher for other crimes, for purposes such as insurance."
Lincolnshire Police said it only classifies rape reports as "no crime" after investigating them.
Det Supt Hatton: "In order to classify something as 'no crime' there must be some credible evidence - rather than we just believe it didn't happen - to suggest to the contrary."
Ms Russell said this made her "deeply sceptical".
"It would certainly be very positive if that was the criteria being applied, but I don't see how they can possibly be applying that measure if they've got a 33% no criming rate for that force," she said.