The Vatican has opened the Holy See’s archives to shed light on the papacy of Pius XII, whose files were kept secret for decades due to accusations he failed to help save Jews during the Holocaust.

Researchers and scholars will be given the opportunity to examine some two million documents spanning the years 1939 to 1958 to glean insight into Pius XII, who was sometimes labelled “Hitler’s Pope”.

Criticism of Pius XII stemmed from his apparent inaction to help Jews facing persecution by Nazi Germany and failing to forcefully condemn the Holocaust.

However, the Vatican insists the controversial pope was a “great champion of humanity” and was “deeply concerned about the fate of humankind during those terrible years”.

Pope Francis made the decision to open up the archives a year ago to prove the Roman Catholic Church was “not afraid of history”.

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Archbishop Paul Richard Gallagher said ahead of the opening that the archives would offer “a comprehensive understanding of what was going on, the type of person he was, the type of policies that Pius XII was issuing in those very terrible years, especially during the Second World War, and of the period immediately afterwards”.

Ronald S Lauder, president of the World Jewish Congress, said in a statement: “In inviting historians and scholars to publicly access the Vatican’s World War Two archives, Pope Francis is demonstrating a commitment to learning and airing the truth, as well as to the significance of Holocaust memory.

“The World Jewish Congress knows that the Vatican was provided on 17 March 1942, a detailed memorandum by the WJC representative in Geneva, Gerhart Riegner, describing brutal evidence of the Nazi’s plan to liquidate the Jews.

“We never heard what happened to Riegner’s memorandum after the papal representative in Switzerland, Messenger Filippe Bernardini, asked for it. But we do know what happened to the six million Jews killed in the Holocaust.

“With the opening of the archives, we may finally learn the truth about what the Vatican knew,” he added.

Mr Lauder was referring to a detailed document that spoke of the Nazis’ plans to hold masses of Jews in concentration camps and the executions of thousands in Nazi-occupied Poland and parts of Russia.

The document, which was handed over by Riegner and Richard Lichtheim of the Jewish Agency for Palestine, said such measures could “perhaps be rescinded or at least alleviated by the intervention of the Holy See”.

Pope Pius XII, wearing the ring of St. Peter, raises his right hand in a papal blessing at the Vatican in September 1945 (AP)

Rabbi Abraham Sorka, who co-authored a book with Pope Francis, wrote in the Vatican newspaper L’Osservatore Romano the opening of the archives would reveal if the Church “could have done something”.

He said: “They should open them and clarify everything. Then it can be seen if they could have done something, to [what] extent it could have been done and if we were wrong in something, we will be able to say: ‘We were wrong in this’.