According to the report, one in 20 victim-based crimes dealt with by Sussex Police in the year ending 30 June 2024 resulted in a charge or court summons.
The report cited a lack of capacity to progress long-standing investigations as a contributing factor to the low number of crimes being solved.
Sussex Police was rated as “good” for its responses to the public and “adequate” in eight other areas of policing, including preventing crime and protecting vulnerable people.
Other issues highlighted in the report included the disproportionality of “stop and searches” carried out by Sussex Police officers.
According to the report, black people were 6.1 times more likely to be subject to a stop and search than white people in the county – higher than the national average rate of 3.6 times for England and Wales.
Ms Shiner said the force was “open to feedback” and that many of the recommendations made in the report had already been identified.
“We will continue working alongside HMICFRS to accelerate and embed these plans to ensure we are delivering the best possible service for the people of Sussex,” she added.