Concerns have been raised over figures revealing just five out of 40 serious sex offences committed in Bury St Edmunds were solved last year.
The statistics released by Suffolk Police show the amount of serious sexual offences - including rape and sexual assault - solved in Bury in 2011/12 fell by 28 per cent compared to the previous year.
In 2010/11, 17 out of 42 were solved - an increase on the seven out of 43 in 2009/10.
The figures were disclosed following a request by County Cllr Mark Ereira-Guyer in preparation for last Thursday’s police and crime commissioner hustings at the Apex.
Cllr Ereira-Guyer, who was chairman of the meeting, said ‘deep concern’ was expressed over the low solve rate.
He said: “We’ve got to ask the police what’s going on there. I don’t know why the rates should be so low.”
In Suffolk, 146 serious sexual offences out of 589 recorded were solved in 2011/12, compared to 154 out of 559 in 2010/11 and 163 out of 586 in 2009/10.
Cllr Ereira-Guyer has forwarded the figures to Bury MP David Ruffley.
A spokesman for Suffolk Police said improving the solved rate of serious sexual offences is a ‘performance priority’.
He added: “We are committed to investigating all reports throughly. Rape and serious sexual offences are extremely distressing for the victims and it is still a largely unreported area of crime.
“We take reports of this nature very seriously and will provide support to victims throughout the investigation and beyond. We have a team of investigators who are specially trained and experienced in dealing with the sensitive nature of sex offences so we would always encourage victims to contact the police or the Sexual Assault Referral Centre.
“Detection rates increase if victims are seen during the seven day ‘forensic window’ but we do not want to discourage anyone from reporting sexual offences, including those that occurred months, or even years in the past.”