Reports of serious sex offences rose by more than a third across Suffolk last year – and less than one in 10 were solved.

Police said an upward trend in victims coming forward had put downward pressure on the solved rate, with more crimes under investigation – and therefore considered ‘unsolved’.

A performance report showed that 1,611 serious sexual offences were recorded last year – up 34.7% on the three-year average.

The figures were published as this paper can reveal that 816 people are currently signing the sex offenders register in Suffolk.

Assistant Chief Constable Rachel Kearton said the increase in reported crime was largely due to victims having more confidence to come forward – particularly in historical sexual offence cases.

The solved rate for 2017 was 8.9% – down 3.8% on average.

On Friday, Police and Crime Commissioner Tim Passmore told a performance and accountability panel he wanted assurance that adequate numbers of staff were in place to bring up the solved rate.

Chief Constable Gareth Wilson said staff levels were within guidelines for all forces, but pointed to a national problem with recruiting detectives internally.

Uniform officers, he said, have set work hours, shift patterns and rest days, and are better remunerated than detectives. But he praised the effort of Detective Chief Superintendent Simon Parkes to plug vacant posts with a direct entry recruitment drive.

“The number of recorded offences is clearly going up,” said Mr Wilson. “But some are made difficult to detect due to the length of time between the offence and someone coming forward.”

Almost 20% of serious sexual offences are reported at least a year after the offence.

Mr Wilson said conviction rates for rape were, historically, far more favourable than those of other forces.

The success of a dedicated rape scrutiny panel had been replicated in other force areas.

The performance report also showed three-quarters of victims supported police investigations, but that investigation was not possible in 4% of cases.

A better solved rate could see an increase in the number of registered sex offenders in Suffolk. There are currently 816 people signing the register – 807 are male and nine are female.

The figures, provided under the Freedom of Information Act, exclude offenders in prison.