Victims and witnesses are suffering as prosecutors make mistakes in more than one in 15 cases and bosses fail to spot the errors, inspectors said today.
A review of standards in the Crown Prosecution Service (CPS) found prosecutors were making "errors of analysis and judgment" which led to 7% of cases being wrongly discontinued or prosecuted.
CPS reviewers, including unit heads, spotted only one in four cases with errors, increasing "anxiety, inconvenience and distress to victims and witnesses" and leading to those who should not be charged facing court.
Inspectors looked at 861 cases and found a clear need for greater rigour and consistency in the quality of managers' assessments.
But they added that the scheme, which was rolled out in 2010, was "helping to drive improvement".
Michael Fuller, chief inspector of Her Majesty's CPS Inspectorate (HMCPSI), said: "Overall standards can only improve if the CPS uses a robust assessment process.
"Early indications are that the new scheme is bringing about a much-needed focus on quality."
The review found that 60 of the 861 cases examined failed the Code for Crown Prosecutors, the test all cases must pass to proceed at key stages.
But CPS reviewers were missing the mistakes, noting only 25% of the cases where one or more featured. Only six of the 32 (19%) charging decision failures and only nine of the 27 (33%) failures at later stages in the case were spotted.
"CPS lawyers are making errors of analysis and judgment, which lead to 7% of cases being wrongly prosecuted or discontinued, and this has significant consequences for victims, witnesses, defendants, criminal justice partners and public confidence," the review said.
"More worryingly, CQSM (Core Quality Standards Monitoring scheme) reviewers are perpetuating these errors by failing to identify the majority of the Code test failures and ensure that lessons are learned; this urgently needs addressing."
It went on: "This shows a significant lack of robustness in challenging key decisions as part of the CQSM process, and is a fundamental flaw in the way that the process is being applied at present.
"From it flow missed opportunities to learn lessons; wasted effort by the CPS and other agencies; unnecessary cost; anxiety, inconvenience and distress to victims and witnesses; adverse impacts for those defendants who should not have been charged; and reputational damage."