Sensational claims of a plot to assassinate Pope Benedict XVI have whipped Italy into a frenzy and focused the world's attention on the poisonous atmosphere seeping through the corridors of the Holy See.

The Italian daily newspaper Il Fatto Quotidiano published an unsigned letter, written in German, which spoke of a Mordkomplott – death plot – against Benedict and quoted the Archbishop of Palermo, Paolo Romeo, as predicting that the Pontiff would die with in 12 months. The anonymous missive, dated 30 December and marked "strictly confidential for the Holy Father" claims to report comments Cardinal Romeo made on a trip to Beijing last year.

It was handed to a papal aide, Cardinal Tarcisio Bertone, last month by Cardinal Darío Castrillón Hoyos of Colombia. The paper did not explain how Cardinal Castrilló* came by the letter, but Marco Lillo, the reporter who broke the story, said German was used to convey the information directly to the Pope, who is German, while throwing prying eyes off the scent.

Yesterday, Cardinal Romeo denied having made such comments. "It is so outside of reality that it should not be given any consideration," he told Italy's Ansa news agency. The Vatican's spokesman, Father Federico Lombardi, was equally dismissive. "It seems to me something that is so far removed from reality that I don't even want to comment on it," he said.

It is a well-known fact that Benedict is unpopular among many Church figures. But experts said the letter was more likely an indication of a plot to cause political mischief than murder.

Robert Mickens, the Rome correspondent of The Tablet, was sceptical. "I rather suspect it is nonsense, written to create even more rancour," he said. "More than anything it is an indication of the ill-feeling there and of the plotting and power struggles."

He noted the anonymous letter may also have been designed to harm the prospects of Angelo Scola, the Archbishop of Milan, who is one of the leading candidates to succeed the 85-year-old Pontiff.