A fact-finding parliamentary committee in the eastern German state of Thuringia on Thursday officially presented its final report on the police investigation into activities of the neo-Nazi group "National Socialist Underground" (NSU).
The NSU is alleged to have carried out at least 10 murders, mostly of people with migrant backgrounds, in Germany, along with other violent crimes.
The around 1800-page report, which was two-and-a-half years in the making, slammed police and justice authorities for a series of mistakes made during the investigation of the crimes.
These included the holding back of important information and a failure to follow up certain paths of inquiry and clues, according to the report.
The report also spoke of glaring deficits in cooperation between different authorities, above all between the Thuringia branch of Germany's domestic security agency and the state's criminal police authority.
The large number of wrong decisions meant that the security authorities had indirectly aided the spread of right-wing extremist structures in Thuringia, the report concluded.
It cited the treatment of a right-wing informer Tino Brandt, saying he had received high payments and had obviously been warned about investigations directed against him.
An earlier report by a Bundestag committee released in August 2013 had also accused investigative agencies of sweeping incompetence and institutional racism.
The interior minister of Thuringia, Jürg Geibert, described the committee's work as an important contribution "to the clarification of this unprecedented case of failure by national and regional authorities."
The NSU is alleged to have killed nine immigrants between 9 September 2000 and 6 April 2006, and a German policewoman in 2007. It has also been blamed for a bombing in the central city of Cologne in 2004, in which more than 20 people were injured, some severely, as well as a number of robberies.
The group went underground in 1998 following the discovery of pipe bombs and explosives in a garage in the eastern city of Jena. The chairwoman of the Thuringia committee, Dorothea Marx, said mistakes made by police in the first six hours after the discovery were "core errors" in the search for the NSU.
Two members of the terrorist trio, Uwe Böhnhardt and Uwe Mundlos, were found dead in November 2011, having presumably committed suicide after a failed bank robbery to avoid arrest.
It was the finding of their bodies that first led police, who had initially assumed that the killers were most likely from the immigrant community, to connect the murders with the NSU.
A third member, Beate Zschäpe, is currently on trial in Munich.
tj/nm (AFP, dpa)