Victims of crime have been sent too many letters containing spelling mistakes, wrong addresses and other errors, inspectors have found.
Letters from the Crown Prosecution Service (CPS) were deemed "unsatisfactory" with more than three quarters not properly written.
The CPS said it was "sorry the quality of our letters has not met the expected standard in every case".
HM chief inspector Kevin McGinty said the CPS was "failing badly".
"It is to be regretted that this report highlights such shortcomings in performance with only 22.1% of letters being rated as being of the expected standard by my inspectors," he said.
Her Majesty's Crown Prosecution Service Inspectorate's (HMCPSI) report said the mistakes would have been spotted if the letters had been properly proof-read.
Of the 340 letters sent by CPS Victim Liaison Units (VLUs) that inspectors looked at, only 75 met the quality standard expected, the report said.
Nearly half of these were rated as being not empathetic enough. Others were sent late.
In some letters details of the wrong case were included, information was inaccurate or the wording was just a "combination of standard paragraphs".
Managers had not been trained in writing letters or responding to complaints, inspectors found.
VLU staff were committed to providing a good service, inspectors said, but an effective level of quality assurance was not in place.
The CPS said it had "already started putting urgent improvements in place including refreshed guidance".
"We are also reviewing our complaints procedure," a spokesperson said.
Six CPS areas were visited by inspectors: North East, South East, South West, Cymru-Wales, Wessex and Yorkshire and Humberside.