Leading Jewish and Roman Catholic scholars are warning against the canonisation of the wartime Pope Pius XII, arguing that he did not do enough to save the Jewish people from persecution by Hitler.

In a letter to be published in The Times today, six senior Catholic academics join three top Jewish scholars in calling for the process towards his beatification to be put on hold.

The Vatican’s Congregation for the Causes of the Saints last year voted in favour of a decree that Pope Pius XII had “heroic virtues”, moving him a step closer to beatification.

Pope Benedict XVI has not yet signed the decree and had appeared to put the process on hold, calling for a “period of reflection.”

But the German-born Pope reignited the controversy, dubbed the “Pius wars”, earlier this month when he praised Pius XII during a Mass in Rome to celebrate the 50th anniversary of his death.

The fears of Jewish leaders around the world that Pius XII might be canonised after all were raised again after Pope Benedict said that the man dubbed Hitler’s Pope by author John Cornwall had saved the “largest possible number of Jews” and had acted silently to avert the worst.

He said: "I am praying that Pius’s progress towards sainthood will continue happily."

In 1942, Pius referred to those condemned to death or progressive extinction “solely because of their nation or race” but failed to refer explicitly to Nazis or the Jewish people.

He refused pleas for help on grounds of neutrality.

Although he privately may have sheltered a small number of Jewish people and encouraged some officials to help others, had he done more, many scholars believe that the murder of more than six million Jewish people in the Holocaust could have been significantly mitigated, such was the influence of the Catholic Church.

As the canonisation moves closer, backed by many conservative Catholics around the world who regard Pius XII as a saintly upholder of tradition and the Gospel and defend him on the grounds of his great personal piety, the row threatens to damage relations between Israel and the Vatican.

Earlier this month, Father Peter Gumpel, the Jesuit relator or “judge” of the Cause for the canonisation of Pius XII, said Benedict XVI would never visit Israel until a panel in Yad Vashem, the Holocaust museum in Jerusalem, was removed.

The panel depicts Pius XII was one of the “Unjust”.

It condemns his failure "to leave his palace, with crucifix high, to witness one day of pogrom". It says that when reports of the massacre of the Jews reached the Vatican, he did not protest either verbally or in writing. The panel continues: “In 1942, he did not associate himself with the condemnation of the killing of the Jews issued by the Allies. When they were deported from Rome to Auschwitz, Pius XII did not intervene."

A few days ago, a photograph of Benedict XVI with a Nazi swastika superimposed was published on a prominent Israeli website, but later replaced with a smiling Benedict in St Peter’s Square after intervention from an Israeli government minister.

The Vatican, which has repeatedly criticised the panel, contradicted Gumpel’s statement and said the display would not be a “determining factor” in any visit.

In their letter to The Times, the scholars, headed by Dr Edward Kessler, of the Woolf Institute of Abrahamic Faiths in Cambridge and Professor John Pawlikowski, of the Catholic Theological Union in Chicago, say that the evidence released so far does not show whether Pius XII acted soon or decisively enough to help the Jewish people.

Calling for more documents from the Vatican archives to be released, they call for the canonisation process to be put on hold until a wider consensus is reached on his response to the Holocaust.