The Gwent office of the CPS was 'weaker' than two years previously
A branch of Wales' Crown Prosecution Service (CPS) has been told to go "back to basics" after a critical report.
CPS Gwent was rated as "poor" by inspectors who said "significant weaknesses" and a "blame culture" had potential to affect public confidence.
The CPS said the HM Crown Prosecution Service Inspectorate (HMCPSI) report "did not make easy reading".
It said changes meant it was delivering "measurable improvements in its services to victims and witnesses".
HMCPSI inspectors first visited the CPS Gwent offices in 2007. The new report was based on another inspection in September 2009.
They concluded the regional office had failed to keep up with the rest of the service, with a lack of leadership and vision leading to strained working relationships with other criminal justice agencies.
The report said inspectors were concerned CPS head office had not more closely scrutinised a branch office already demonstrating serious management failings.
It said the CPS Gwent service was in a "much weaker position" than in 2007, with the failings having an impact on the service offered to victims and witnesses and the quality of justice overall.
Crown court cases, including serious violence, sexual offences and hate crime had poor preparation and decision-making, while victims' needs were not always paramount, the report said.
It said the service's blame culture, "readily" demonstrated in open court, had the potential to affect public confidence in the criminal justice system in a part of the country where it was already low.
However, they found cases before magistrates were made difficult for prosecutors by files from police which were often of poor quality and unacceptably delayed.
Even then, the report said, "wrong decisions are being made" with cases being discontinued "even though there is no material change in circumstances".
Inspectors said no internal performance management system picked up what was happening.
Chief inspector of the CPS Stephen Wooler said: "It is deeply disappointing to find CPS Gwent in such a weak position.
"Many of the issues which were identified previously remain, and in some cases have been exacerbated by further management failings.
"In short, the area must go back to basics. I have discussed with the new chief crown prosecutor the problems faced by the area.
"Although a new approach is beginning to have a significantly positive impact, the task ahead should not be underestimated.
"It will take some time for the service offered in Gwent to begin to meet the required standards."
Inspectors praised CPS staff for their hard work and enthusiasm, saying the last two years had been demoralising for them.
Jim Brisbane, the Gwent service's new chief crown prosecutor, acknowledged the shortcomings inspectors highlighted.
He said: "Even before the inspection process had been completed, we had started to put in place a robust and wide-ranging set of plans to improve all aspects of our service.
"I am reassured to know that the areas for improvement identified by the inspectors are those that we are already addressing.
Gwent Police chief constable Mick Giannasi, chairman of the Gwent Criminal Justice Board, said the area was "moving into a new era of co-operation".