Pope Benedict XVI urged an end to "religious hypocrisy" and "rivalry" in the Catholic Church as he donned his papal mitre for the last time for an emotional mass in St. Peter's Basilica on Wednesday.
The 85-year-old pope was hailed with a standing ovation and waves of applause from a congregation of thousands where many broke down in tears, as cardinals doffed their mitres in a final gesture of respect.
Wearing the purple robes of Lent -- a period of penitence for Christians -- the pope was conveyed through the basilica's vast nave on a mobile platform that underlined his growing infirmity.
Benedict called for greater sincerity in his final mass as leader of the world's 1.2 billion Catholics before he becomes only the second pontiff to resign voluntarily in the Church's 2,000-year history.
He condemned "religious hypocrisy" and urged an end to "individualism and rivalry".
"The face of the Church... is at times disfigured. I am thinking in particular of the sins against the unity of the Church," he said, a possible reference to the many scandals plaguing the institution.
Christ "denounces religious hypocrisy, a behaviour that seeks applause and approval. The true disciple does not serve himself or the 'public', but his Lord, in simplicity and generosity," Benedict said.
The pope cut short the applause at the end of mass, saying "Let's return to prayer", before leaving the basilica, waving and smiling at the congregation.
Earlier Wednesday, the frail pontiff was greeted by chants of "Benedetto" and a banner reading "Thank You, Holiness" at his weekly audience with thousands of believers in a Vatican auditorium.
Benedict told the crowd he had taken his momentous decision "for the good of the Church".
"Keep praying for me, for the Church and for the future pope," he said, his voice full of emotion.
Wearing his workaday white cassock and skullcap, the pontiff said he could feel the faithful's love "almost physically in these difficult days".
The Vatican announced that cardinal electors -- the princes of the Church -- will meet on March 15 or soon after to choose Benedict's successor.
"The beginning of the conclave cannot be before March 15," Vatican spokesman Federico Lombardi told a press conference. "We have to expect a conclave starting on the 15th, 16th, 17th, 18th or 19th."
The secret conclave held in the Sistine Chapel under Michelangelo's famed ceiling frescoes -- deliberations that normally last a few days -- should produce a new pope in time for Easter.
Many ordinary Catholics have said they would like the new pope to be more in tune with the times after the traditionalist reigns of Benedict and his long-time predecessor John Paul II.
"I want someone who is youthful and with a youthful spirit who can be more flexible," said Ieva Tamosaityte, 25, a Lithuanian musician in the congregation at the pope's last mass.
"I would like future popes to retire when they get old too," she said, as staff in the basilica distributed photos of the outgoing pope.
Rumours have begun flying over front-runners to succeed Benedict, but no clear favourite has emerged yet and the decision will be up to the 117 elector cardinals.
While some hope that Africa or Asia could yield the next pontiff, others have tipped high-flying European or North American cardinals.
Benedict announced on Monday that he would resign because he no longer had the strength to carry out his duties.
Although the Vatican has denied that specific health problems influenced his decision, it said Tuesday he had a secret operation to replace the batteries in his pacemaker three months ago.
Benedict will no longer be pope from 1900 GMT on February 28, after which, as Lombardi put it, "people will know they no longer have to go to him for questions regarding the Universal Church."
Shortly before the time runs out on his papacy, a helicopter will whisk Benedict away to the papal summer residence in Castel Gandolfo near Rome where he will live temporarily while his new permanent residence in the Vatican is being renovated.
Benedict will honour his existing engagements in the final days of his papacy, with a few notable exceptions like meetings with Italian President Giorgio Napolitano and Prime Minister Mario Monti.
Benedict's resignation has eclipsed campaigning for the February 24-25 election in Italy, with analysts saying it could have a major impact on the outcome -- perhaps stopping scandal-tainted billionaire Silvio Berlusconi's rise in the polls.
At the Vatican, next week will be given over to a spiritual retreat which is sure to be dominated by jockeying among factions within the College of Cardinals over the choice of Benedict's successor.
The pope will hold his final general audience on February 27, this time a farewell event for all in St. Peter's Square, before retiring to a little-known monastery within Vatican walls, just a stone's throw away from his successor.
Asked about this unprecedented "cohabitation", Lombardi replied: "I think the successor and the cardinals will be very happy to have very close by the person who best of all can understand the spiritual needs of the Church."
Only one other pope has resigned voluntarily -- Celestine V in 1294 -- a humble hermit who stepped down after just a few months saying he could no longer bear the intrigues of Rome.
The new pope will have to face up to growing secularism in the West, one of the Church's biggest challenges.
Benedict admonished Wednesday: "You cannot be Christians as a simple consequence of living in a society with Christian roots."
He added: "Even those born into a Christian family and given a religious education should... put God first in the face of the temptations that a secular culture presents all the time."
Pope Benedict XVI waves as he leaves after celebrating Mass on February 13, 2013 at St Peter's basilica at the Vatican. Pope Benedict XVI urged an end to "religious hypocrisy" and "rivalry" in the Catholic Church as he donned his papal mitre for the last time.
This picture shows the sunset over St Peter's Basilica on February 13, 2013 at the Vatican.
Pope Benedict XVI (C) leads the mass on February 13, 2013 at St Peter's Basilica at the Vatican.
Pope Benedict XVI waves after celebrating Mass on February 13, 2013 at the Vatican.