Prosecution lawyers have been criticised for failing to inform crime victims when charges against a suspect are dropped or changed.
Rape victims were among those not notified of changes
The Crown Prosecution Service Inspectorate said victims were not sent a letter in almost a third of the cases they examined in England and Wales.
The CPS must write to crime victims about decisions in their case within five days.
The Director of Public Prosecutions said the problem was being addressed.
Notifying victims within five days is part of the government's drive to improve the way victims are treated, but inspectors found some victims were not told charges had been dismissed until after the court hearing, several weeks later.
Rape victims were among those who did not receive any communication - a matter of "real concern" said the inspectorate.
Some letters used legal terms, such as "formal acquittal" and "bind over", without explanation; others were insensitively worded; or were addressed "Dear Sir/Madam", giving them a "computer-generated" feel.
The Director of Public Prosecutions, Sir Ken Macdonald, said "urgent work" has begun to address the issues raised.