Specialist rape squads could be set up to improve Sussex Police’s success rate in investigating the crime.

The force is lagging behind the rest of the country in the number of sex offences it solves and has been advised to find ways to improve.

The Argus can reveal not one of 12 public place sex attacks which prompted detectives to appeal for the public’s help last year has been solved.

In 2011/12 there were 1,467 sex assault cases in Sussex – roughly one per thousand people.

The force had a “sanction detection” rate – where a person is charged or cautioned or fined – of 27% of sex assault cases, against a national average of 30%.

In 2010/11, the figure was 29% against the same national average.

That year Sussex Crown Prosecution Service succeeded in 64 out of 115 prosecutions for rape – 55% – compared with 79% of other sex offence cases and 89% of burglary cases.

Sussex Police’s Detective Inspector Miles Ockwell is carrying out a six-month review of the way rapes are investigated by the force.

He is also reviewing treatment of other specialist areas like child abuse, domestic violence and dealing with serious offenders after their release from prison.

At the moment, most rapes and serious sex assaults are dealt with by non-specialist CID officers, with specialist sex offence liaison officers working with victims.

The Surrey and Sussex major crime investigation team is tasked with taking on the most serious “stranger” cases.

Last year the National Policing Improvement Agency recommended the force look into creating specialist units in the county to deal with rape and sexual assault.

Detective Superintendent Nev Kemp, head of Sussex Police’s Protecting Vulnerable People branch, said: “The project draws together a number of reports and recommendations aimed at modernising and strengthening our local specialist and criminal investigative functions.

“A central aim of the project is to further improve the service we provide to victims of these offences while maintaining our overall capacity and resources.

“This work is not about reducing the level of resources we devote to these crucial areas of policing but is about ensuring that we maximise our effectiveness.”

The cases The Argus highlights today were all subject to appeals for information from the public.

The vast majority involved claims strangers had committed crimes in public places.

Detective Chief Inspector Carwyn Hughes said it is important victims call police as soon as possible after they are attacked.

He said: “We successfully conclude many rape and serious sexual offences investigations and prosecutions but are the first to accept that we cannot always achieve this.

“However year on year people are becom- ing more confident in reporting incidents of serious sexual assault and rape to us and we are solving more than before.

“Investigations can be complicated when allegations are not reported at the time, as this can lead to a loss of valuable forensic evidence.”

Sussex Police pledged in a statement to treat victims with dignity and respect and take all rape or sex assault claims seriously.