VATICAN CITY: Pope Benedict XVI will have the official title of "pope emeritus" and continue wearing the papal white cassock after he resigns on Thursday -- the first leader of the Catholic Church to do so since the Middle Ages, the Vatican said.

Benedict can still be addressed as "Your Holiness Benedict XVI" and will have the additional title of "Roman pontiff emeritus", spokesman Federico Lombardi told the Vatican press corps on Tuesday.

Benedict can also still wear a white cassock normally reserved only for pontiffs -- but without the doubled shoulder cape -- and has chosen to swap his trademark red shoes for a brown pair given to him by artisans in Mexico during a trip last year, Lombardi said.

The Vatican spokesman also said that a series of meetings of cardinals to settle on a date for the start of a conclave to elect Benedict's successor could start on Monday.

Lombardi said the pope had already sorted through official documents from his papacy that will remain in the Vatican and personal notes that he will take with him into retirement.

Benedict holds a final general audience in St Peter's Square on Wednesday, the eve of his resignation from a troubled eight-year papacy dominated by paedophile priest scandals and Vatican intrigue.

At least 50,000 pilgrims are expected to attend, enough to fill the famous square to overflowing.

On Thursday at around 5:00 pm (1600 GMT), the pope will be flown by helicopter to Castel Gandolfo, the traditional summer residence of popes.

Lombardi said no fanfare will mark the official end of his papacy at 8:00 pm, other than the handover of responsibility for his security from the Swiss Guard to Vatican police.

"The symbolic moment will come when the gates (of Castel Gondolfo) close at 8:00 pm and the Swiss Guard leave in a symbolic departure," Lombardi said.

The 85-year-old German pontiff shocked the world when he announced on February 11 that he would step down at the end of the month, citing his age and failing strength.

Asked whether Benedict will be the first former pontiff to be called "pope emeritus", Lombardi laughed and said: "We don't know what Celestine V was called when he stepped down. We'll have to ask the historians."

The 13th-century monk was the only other pope in the 2,000-year-old Church's long line of rulers to step down voluntarily -- saying he could not tolerate the intrigues of the Church hierarchy.