Pope Benedict XVI has vowed “unconditional obedience and reverence” to his successor.

The pontiff was speaking on his final day in office at the Vatican to his cardinals, one of whom will be elected next month to replace him.

Pope Benedict, 85, will leave for the papal retreat at Castel Gandolfo, near Rome, later on Thursday.

His deputy, Cardinal Tarcisio Bertone, will have temporary charge of the world’s 1.2 billion Roman Catholics.

In his public farewell speech on Wednesday, Pope Benedict hinted at Vatican infighting.

His decision to resign has been openly criticized by Australia’s top Catholic, Cardinal George Pell, who questioned his leadership skills.

The Church has been beset by scandals over sexual abuse by priests and leaked confidential documents revealing internal corruption and feuding.

An estimated 150,000 people packed into St Peter’s Square on Wednesday to hear Pope Benedict, resigning at 85 after seven years in office.

The long-time theologian is expected eventually to retire to a monastery on a hill inside Vatican City, with officials saying he will not be able intervene publicly in the papacy of his successor, though he may offer advice.

His successor must focus on reforming the Vatican bureaucracy, which has often been overly hesitant to react to the various crises which have arisen during Benedict’s papacy.

Pope Benedict received cardinals for a farewell ceremony on Thursday morning, warmly embracing Cardinal Angelo Sodano, who passed on best wishes on behalf of those gathered.

“Among you there is also the future pope to whom I promise my unconditional obedience and reverence,” the pontiff told those assembled.

“The Church is a living being,” he added, but it “also remains always the same”.

He is later due to say goodbye to his staff before being taken to a helipad for the 15-minute flight to Castel Gandolfo.

The residence, 15 miles (24 km) south-east of the Italian capital, is the traditional summer home of the popes.

Pope Benedict XVI has vowed “unconditional obedience and reverence” to his successor

At 20:00 local time, Benedict will cease to be pope, a moment which will be marked symbolically when the Swiss Guards at the gate of Castel Gandolfo march off for their return to the Vatican.

The German pontiff, who was born Joseph Ratzinger, will continue to be known as Benedict XVI, with the new title of “pope emeritus”.

In his retirement, he will wear a simple white cassock rather than his papal clothes and swap his famous red shoes – the color is symbolic of the blood of the early Christian martyrs – for brown.

His “Fisherman’s Ring”, the special signet ring which contains the Pope’s name and is impressed to validate certain official documents, is expected to be destroyed along with the lead seal of the pontificate.

Addressing the crowd in St Peter’s Square on Wednesday, Pope Benedict thanked believers for respecting his decision to retire and said he was standing down for the good of the Church.

“There were moments of joy and light but also moments that were not easy,” he told the crowd.

“There were moments, as there were throughout the history of the Church, when the seas were rough and the wind blew against us and it seemed that the Lord was sleeping.”

Speaking from Rome, Cardinal George Pell told a TV channel that while Benedict was a “brilliant teacher”, “government wasn’t his strong point”.

“I think I prefer somebody who can lead the Church and pull it together a bit,” he told the Seven Network.

The first resignation of a pope since the Middle Ages, he suggested, had set a worrying precedent for the Church: “People who, for example, might disagree with a future pope will mount a campaign to get him to resign.”

Cardinal George Pell, 71, is among the 115 cardinal-electors (those younger than 80 years old) eligible to vote for the new pope, and theoretically could be chosen himself, though he has played down the possibility.

From March 4, the cardinals will meet for talks at which they will set a date for the start of the secret election, or conclave.

A two-thirds-plus-one vote majority is required. Sixty-seven of the electors were appointed by Benedict XVI, and the remainder by his predecessor John Paul II.

About half the cardinal-electors (60) are European – 21 of them Italian – and many have worked for the administrative body of the Church, the Curia, in Rome.

Events on Thursday:

• About 16:15: Benedict is driven to a helipad within the Vatican
• About 17:00: Papal helicopter flies to Castel Gandolfo near Rome
• About 18:00: Pope appears at a window overlooking the public square in Castel Gandolfo to bless a crowd
• About 20:00: Benedict ceases to be pope; Swiss guards at the entrance to Castel Gandolfo leave their posts