Shocking figures show nearly 13,600 crimes in Hyndburn over the past five years have gone unsolved, the Observer can reveal.

Unsolved rapes in the borough have nearly doubled over the past two years while unresolved sexual offences have also risen by a third.

The number of rapes reported in the borough rose to 15 last year from eight in 2012.

The figures released by Lancashire Police under the Freedom of Information Act also show unsolved shoplifting cases have more than doubled from 67 in 2009 to 146 in 2013 along with non-house burglaries, up from 242 to 348 over the same period.

The highest category of unsolved crimes is criminal damage and arson with 3,570 over the five years, however the numbers have steadily fallen.

Superintendent Damian Darcy said they are working ‘extremely hard’ to bring all offenders to justice.

He said: “Unfortunately, some crimes remain undetected and there can be many reasons for this.

“It may be because the victim does not wish to pursue a prosecution; there are no witnesses or forensic opportunities, or restorative justice has been used which some of the figures fail to reflect.”

Detective Chief Inspector Neil Esseen said they will do ‘everything possible’ to trace rape and sexual assault offenders.

He said: “Most of the reports of rape that we receive are committed by someone that the victim knows in some way – incidents of stranger rape are very rare.

“Many factors can often make it hard for a victim of rape to want to report the crime.

“Even when they do, they can then find it difficult to want to progress this through the court system and sometimes there is insufficient evidence to take cases to court.”

Clive Grunshaw, Lancashire Police and Crime Commissioner, said the constabulary needs to avoid ‘complacency’.

He said: “The public of Lancashire rightly expect Lancashire’s officers to perform highly and I am committed to ensuring standards are maintained.

“I can reassure residents that I will not accept complacency and will continue to demand the highest levels of performance from the constabulary.”

Hyndburn Council leader Miles Parkinson said more resources needed to be channelled to tackling serious crimes.

He said: “Everyone would want all crimes solved but unfortunately that’s not going to happen.

“The concern is when crimes of a serious nature are not being resolved and there can be reasons for that.

“The limited resources of the constabulary should be focused on more serious crimes.

“That’s not saying criminal damage and burglary are not important because they have a dramatic effect on people and their property.”

Tory councillor Peter Britcliffe said he was ‘surprised’ by the figures.

He said: “I am rather surprised at how high these figures are.

“We’re told that crime is reducing so hopefully that would mean unsolved ones are going down too.”