The Vatican's official newspaper has accused Britain and the United States of having detailed knowledge of Hitler's plans to exterminate the Jews but of failing to do anything to halt the Final Solution.
L'Osservatore Romano said the British and American governments ignored, downplayed or even suppressed intelligence reports about the Nazis' extermination plans.
They could have bombed Nazi concentration camps and the railways that supplied them but instead chose not to, the newspaper claimed.
It quoted from the diary of Henry Morgenthau Jr., the wartime US secretary of the treasury, who described London's alleged indifference to the plight of the Jews as "a Satanic combination of British chill and diplomatic double talk, cold and correct and adding up to a sentence of death".
British and American inaction was in contrast to the efforts made by the wartime Pope, Pius XII, who tried to save as many Jews as he could through clandestine means, L'Osservatore claimed in a lengthy article titled "Silence and omissions at the time of the Shoah (Holocaust)".
The editorial is the Vatican's latest effort to rehabilitate the reputation of Pope Pius, whose reluctance to denounce the Nazis publicly prompted accusations of anti-Semitism and earned him the title "Hitler's Pope".
L'Osservatore dismissed such claims as a "radically false" characterisation of the pontiff's wartime record.
It quoted Morgenthau as saying that as early as Aug 1942, the US government "knew that the Nazis were planning to exterminate all the Jews of Europe".
In his diary, Morgenthau cited a telegram dated Aug 24, 1942, and passed on to the US State Department, that relayed a report of Hitler's plan to kill between 3.5 million and four million Jews, possibly using cyanide poison.
L'Osservatore, which is regarded as the semi-official mouthpiece of the Holy See, reproduced a copy of the telegram.
American officials had "dodged their grim responsibility, procrastinated when concrete rescue schemes were placed before them, and even suppressed information about atrocities," Morgenthau wrote.
When the US government was finally convinced to try to rescue European Jews who had not already been sent to concentration camps, the British baulked, the editorial said.
It cited a British Foreign Office cable that warned of "the difficulties of disposing of any considerable number of Jews should they be rescued from enemy occupied territory" and advised against allocating money for the project.
While the British and Americans prevaricated, Pius was engaged in "the only plausible and practical form of defence of the Jews and other persecuted people" by arranging for them to be hidden in monasteries, convents and other Catholic Church institutions, the newspaper claimed.
L'Osservatore said that although the Nazis rounded up and deported from Rome more than 2,000 Jews, another 10,000 were saved.
Marking the 50th anniversary of Pius' death last year, Pope Benedict XVI described him as a great pontiff who worked "secretly and silently" during the war to "save the greatest number of Jews possible".
Sir Martin Gilbert, the British historian and biographer of Winston Churchill, described in his 2001 book "Auschwitz and the Allies" how an underground network of European Jews had begged the RAF to bomb Auschwitz.
Churchill, who had told Anthony Eden in 1944 that the Holocaust was probably the greatest crime ever committed in human history, had given his permission for raids to go ahead.
"Yet even then a few individuals scotched the Prime Minister's directive because, as one of them put it at the time, to send British pilots to carry it out would have then risked 'valuable lives'," wrote Sir Martin.
"At that very moment, however, Allied lives were being risked to drop supplies on Warsaw during the Polish uprising and during these missions these very same pilots had actually flown over the Auschwitz region on their way to Warsaw."