FRANKFURT — Volkswagen’s attempt to remake its company culture and become more law abiding has received poor grades from the former United States prosecutor who is enforcing the carmaker’s compliance with a deal that settled emissions cheating charges.

The German carmaker acknowledged on Sunday that a progress report found that it had failed to hold executives accountable for wrongdoing that led to the huge emissions fraud, and that it was not making a serious enough attempt to remake its culture. The report was prepared by Larry Thompson, a former United States attorney who later spent several years as deputy attorney general during President George W. Bush’s administration.

The conclusions of Mr. Thompson’s confidential report, first reported by the Bild am Sonntag newspaper and confirmed by a Volkswagen spokesman, are the latest sign that a ballyhooed campaign by Volkswagen to become an exemplary corporate citizen has been floundering.

Last week, nearly 200 German police officers and prosecutors raided offices of Porsche in Stuttgart and other locations, seizing documents as part of an investigation into what role the sports car maker, a division of Volkswagen, may have played in a conspiracy to conceal excess diesel emissions from regulators.