The American government provided a safe haven for Nazis after the Second World War, according to a Department of Justice report kept secret for four years.

"America, which prided itself on being a safe haven for the persecuted, became in some small measure a safe haven for persecutors as well," the 600-page report concludes.

The Department of Justice fought the release of the report since it was completed four years ago.

Last month, it released a heavily redacted version. But a full version was published by the New York Times at the weekend.

In addition to chronicling government support for former Nazis living in America, the report also revealed odd details. They included the fact that the director of the Justice Department's Nazi hunting unit, the Office of Special Investigations (OSI), kept Joseph Mengele's scalp in a desk drawer.

The CIA comes off particularly badly in the report.

It reveals that the agency debated whether to cover up the Nazi past of Otto Von Bolschwing, a high-ranking SS officer and associate of Adolph Eichmann, when he applied for US citizenship.

The agency eventually decided he should admit he was a Nazi. Though it is unclear whether agents realised that Von Bolschwing served as chief SS intelligence officer in Romania and Greece during the war.

The report also suggests CIA officials may have withheld information from the OSI in the case of Tscherim Soobzokov.

The Justice Department tried to extradite Soobzokov during the 1980s. It based its extradition on the claim that Mr Soobzokov covered up his Nazi past when he applied for citizenship.

The extradition case was dismissed when Mr Soobzokov produced documents showing that he had declared his Waffen SS membership.

The Justice Department report reveals that the CIA had a copy of the document but removed it from Mr Soobzokov's file.

In the case of Mengele, the Auschwitz camp doctor known as the Angel of Death, the report reveals that there were doubts that a body located in Brazil in 1979 was that of Mengele.

So OSI director Eli Rosenbaum kept a piece of Mengele's scalp in his office until DNA analysis techniques were advanced enough to prove beyond doubt that the body was Mengele's.

Rabbi Marvin Hier, founder of The Simon Wiesenthal Centre in Los Angeles, said he was troubled that the Justice Department would not clarify what those errors and omissions are.

"In the report so far we haven't found anything that could be called a shot heard around the world," Rabbi Hier said.

"But when the Department of Justice says its report is not complete, that means there is the possibility they are holding something back that may be a revelation."