The number of rape charges in Norfolk is falling despite reports rising four-fold in the last six years.

The multi-agency Rape Monitoring Group (RMG) has published data showing how cases of rape were dealt with at all stages of the criminal justice system in 2017/18.

In Norfolk, the number of rapes reported to Norfolk Police has risen from 214 in 2012/13 to 831 in 2017/18.

Just 30 of the 169 cases sent to the CPS for a charging decision were charged, with 40 successful convictions in that year.

Earlier this month chief constable Simon Bailey said the number of rape prosecutions were a "disgrace".

He cited delays in bringing cases to court and investigative problems in non-recent cases.

"There is a real challenge at this moment in time in terms of maintaining and securing the confidence of victims because of the amount of time it is taking to investigate these matters," he said.

"There is issues around CPS availability to deal with the review of the files and the test they are applying.

"There is no doubt we have seen a reduction in files being transferred to the CPS and that is something I am looking at through my public protection work.

A Norfolk Police spokesperson said "many factors" have an effect on conviction rate, including the "disproportionately low" levels of victim engagement.

They added a detective sergeant has been assigned in a quality assurance role since January last year to make sure a case is sound before it is presented to the CPS.

"We are committed to helping victims of rape and serious sexual offences achieve the best possible outcome and to recover from the trauma they have experienced," the spokesperson said.

"Nationally there is a wholesale government review of police, prosecutor and courts' response to the deepening gap between reporting of, and successful prosecutions for, rape. "Norfolk Constabulary and the National Police Chief's Council are supporting this piece of work.

"Many factors have an effect on conviction rate. It is important to note that while the growth in reports of crimes of this nature reflects an increased confidence from victims in coming forward, often when dealing with issues such as domestic abuse or sexual offences, victims are not always in support of prosecution and wish for a different outcome.

"Rape and sexual assault cases are some of the most complex crimes that police deal with. "Part of this work focuses on increasing victim engagement levels, which are disproportionately low when compared to other crime types. In order to achieve this, we are working closely with our partners from the Harbour Centre (Sexual Assault Referral Centre) to promote their bespoke independent service."

In addition to sexual violence advisors at the Harbour Centre, Norfolk Police said they are commissioning an interview advisor to provide the "best response" to victims of sexual assault.

"We hope to see fewer disengagements with the criminal justice process as victims secure a more bespoke service to their individual needs and circumstances," said the spokesperson.