Prosecutors are failing to deal with routine cases properly and the percentage of successful rape convictions has dropped for the first time in three years, inspectors have found.
Chief inspector of the Crown Prosecution Service Michael Fuller found that while handling of more serious cases is good, so-called "volume crime", such as burglary, street robbery and car crime, is suffering.
He said: "Overall, the CPS handles its most serious and complex casework well, but the position is less satisfactory in what is referred to as 'volume crime' cases.
"They still need proper care and attention and I am not assured that this is happening routinely."
His team looked at a sample of 776 files, mostly cases that were finalised between March and July last year.
They found that despite better handling of rape cases, the proportion of successful outcomes dropped from 63.2% to 60.3%, bucking the trend over the previous three years.
The report said: "It is of concern that despite better case handling, the proportion of successful outcomes in rape cases has declined from 63.2% to 60.3%, reversing the positive trend in outcomes over the previous three years."
There were also fears about the quality of cases where police bring charges, with 83.1% reaching required standards compared with 87.4% the previous year.
A third of these cases were still allowed to go to trial by the CPS.
The report said: " There would still have been an unsuccessful outcome if they had been discontinued promptly, but valuable resources would not have been wasted, nor would the victims' expectations have been unrealistically maintained."
The report found that the CPS is suffering from budget cuts, and since 2011/12 has lost 450 prosecutors and nearly 500 administrators.
In 2013-14 only 74.4% of magistrates' court sessions were covered by CPS prosecutors compared with 80.0% in 2012/13.
Inspectors found that prosecutors had an appropriate "grip" on 46.3% of the cases assessed, compared with 53.7% the previous year.
This is a broad measure of adherence with court rules and legal procedures.
Director of Public Prosecutions Alison Saunders said: "I welcome the Inspectorate's acknowledgement that we have improved our performance on serious and complex cases, and also that it has highlighted our success in hate crime cases and those involving violence against women and girls; the police and CPS are now working hard together to advance our handling of rape cases to return to the long term trend of increasing conviction rates.
"This report is largely based on cases completed more than a year ago, however, and more recent data shows performance improvements across the board since then. For example, magistrates' courts are seeing more guilty pleas and fewer cases dropped while the Crown Courts are showing increasing conviction rates - now at 81% across England and Wales - and a marked rise in our timely compliance with judges' orders.
"While the challenges mentioned in this report are ones we are addressing they should be seen in the context of an improving prosecution service across the country. The public can have confidence in our performance and also my determination to bring further improvements where they are needed."