BERLIN — Germany’s police and security services suffered from deeply rooted prejudices and a lack of cultural diversity, which allowed a neo-Nazi cell to carry out violent attacks against immigrants for more than a decade without being detected, according to a parliamentary committee report issued Thursday.

The parliamentary investigation was ordered after the police in November 2011 stumbled on a link between a bungled bank robbery and the unsolved murders of nine small-business owners — eight Turks and one Greek — between 2000 and 2007. The realization that a three-member cell of neo-Nazis operated in Germany for years with impunity caused public outrage and led to the resignation of top law enforcement officials.

The inquiry concluded that prejudice often led the police to draw quick and erroneous conclusions about certain murders, based on the ethnicity of the victims, and it demanded changes in the 36 law enforcement agencies, including training and recruiting more ethnic minorities.

“Turks murder Turks — that seems to have been the mentality,” said Sebastian Edathy, a lawmaker from the center-left Social Democratic Party who was chairman of the committee. “I don’t think it is a case of institutional racism, but we do have racists working within the security authorities.”