Large crowds packed St Peter's Square in Rome overnight for Pope Benedict's final Sunday address before he steps down on Thursday.
The Pope told the gathering his decision to retire did not mean he was abandoning the Catholic Church.
But his last days in the job are being overshadowed by a new scandal involving the UK's most senior Catholic.
Cardinal Keith O'Brien, leader of the Catholic Church in Scotland, is accused of acting inappropriately towards other priests 30 years ago.
Britain's Observer newspaper reported that the allegations, by three priests and a former priest, were sent to Rome a week before the pope's resignation.
"The Pope is informed about the problem and the matter is now in his hands," Vatican spokesman Federico Lombardi told journalists when asked about the report.
A spokesman for Cardinal O'Brien said the claims were contested.
The four claimants, from the diocese of St Andrews and Edinburgh in Scotland, reported to nuncio Antonio Mennini, the Vatican's ambassador to Britain, that O'Brien had committed "inappropriate acts" going back 33 years, the Observer said.
One priest claimed he received unwanted attention from the cardinal after a late-night drinking session. Another alleged that Cardinal O'Brien used night prayers as cover for inappropriate contact, according to the paper.
Cardinal O'Brien has a vote in the papal conclave which is due to pick a new pope next month.
The claimants, who are demanding the cleric's resignation, are worried that their report will not be properly addressed if he is allowed to travel to Rome.
"It [the church] tends to cover up and protect the system at all costs," said one of the complainants, according to quotes published by the Observer.
"The church is beautiful, but it has a dark side and that has to do with accountability. If the system is to be improved, maybe it needs to be dismantled a bit."
Cardinal Cormac Murphy-O'Connor, the former archbishop of Westminster and ex-head of the Roman Catholic Church in England and Wales, said Cardinal O'Brien should still be allowed to help choose the next pope if he chooses.
"The cardinal has denied the allegations, so I think we will just have to see how that pans out," he told BBC television.
The Sunday address was one of Benedict's last appearances as pontiff.
"The Lord is calling me to climb onto the mountain, to dedicate myself even more to prayer and meditation," he said to cheers of "Long Live the Pope".
"But this does not mean abandoning the church.
"Actually, if God asks this of me, it is precisely because I can continue to serve her with the same dedication and the same love I have shown so far."
On Wednesday, he will hold his last general audience in St Peter's Square and on Thursday he will meet with cardinals and then fly to the papal summer retreat south of Rome.
The papacy will become vacant at 8pm (Rome time) on Thursday.
Cardinals will begin meetings the next day to prepare for a conclave, likely to start in mid-March, where they will elect a new pope from among themselves.