Leicestershire's Crown Prosecution Service has been given a "poor" rating, the lowest possible ranking, after its latest government inspection.
The service stayed "stable" in three areas but there were clear signs of decline in eight, including the level of service given to victims.
The county's Chief Crown Prosecutor, Kate Carty, said she was disappointed but the situation was improving.
The inspection of the service was carried out in April 2007.
Ms Carty, who joined the service six months after the inspection was carried out, said: "It is disappointing as it is, in a way, ancient history and we've moved on in leaps and bounds since April 2007.
She added: "Our reputation will be affected by this performance assessment."
The report, following an inspection carried out by the HM Crown Prosecution Service Inspectorate (HMCPSI), also found that despite an improvement on the previous year, the conviction rate of 80.7% was "significantly below the national average" of 84.3%.
The report said the CPS in Leicestershire had seen a "limited improvement in handling of cases in magistrate's court".
The report did acknowledge that problems were beginning to be addressed and Ms Carty's appointment would help "consolidate changes being implemented".