Between 2005 and 2007, a number of failings were alleged in the procurement arrangements operated by Roads Service in relation to the supply, delivery and erection of Road Signs.
The Department for Regional Development subsequently conducted an investigation and issued a report in 2010.
Stewart Dickson MLA said: “This Audit Office Report is a damning indictment of the actions of Departmental officials. Particularly concerning are claims that there was a lack of desire by officials to establish the truth.
“I am also disturbed by findings that the investigation was poorly planned and that various potential sources of evidence were not accessed.
“I sincerely hope that the Department takes on board the findings of this report and ensures that any future investigations are treated seriously and carried out in a full and professional manner.”