The Pope has expressed his "deep sorrow and shame" in a meeting with five survivors of clerical sex abuse.
The Catholic Church said the Pontiff had met five victims at the home of the Vatican's Ambassador to the UK in Wimbledon, south west London.
"He was moved by what they had to say and expressed his deep sorrow and shame over what victims and their families had suffered," a statement from the Holy See said. "He prayed with them and assured them that the Catholic Church is continuing to implement effective measures designed to safeguard young people, and that it is doing all in its power to investigate allegations, to collaborate with civil authorities and to bring to justice clergy and religious accused of these egregious crimes."
The meeting came after the Pope apologised for the "unspeakable crimes" committed by Catholic priests who sexually abused children. In the most strongly-worded public apology of his state visit so far, the Pontiff spoke at Westminster Cathedral of the "shame and humiliation" brought by the scandal.
He told the congregation: "I think of the immense suffering caused by the abuse of children, especially within the Church and by her ministers. Above all, I express my deep sorrow to the innocent victims of these unspeakable crimes, along with my hope that the power of Christ's grace, his sacrifice of reconciliation, will bring deep healing and peace to their lives. I also acknowledge with you the shame and humiliation which all of us have suffered because of these sins."
The private meeting is the fifth time the Pope has met survivors of clerical sex abuse.He has met victims of clerical abuse in the US, Australia, Rome and in Malta earlier this year where he was reportedly reduced to tears.
A Catholic Church spokeswoman said three of the victims at the private meeting were from Yorkshire, one from London and one from Scotland. One of the victims is understood to have suffered the abuse in an Irish institution.
Earlier, the Pope met Prime Minister David Cameron, Deputy Prime Minister Nick Clegg and acting Labour leader Harriet Harman.
He also held his first-ever meeting with child protection professionals at St Peter's Residence - a south London care home for the elderly. In a statement after the private meeting, he said: "It is deplorable that, in such marked contrast to the Church's long tradition of care for them, children have suffered abuse and mistreatment at the hands of some priests.We have all become much more aware of the need to safeguard children, and you are an important part of the Church's broad-ranging response to the problem."
Later on Saturday evening, a crowd of 80,000 people descended on London's Hyde Park for an evening prayer vigil with the Pope, with dancing nuns, singing priests and happy families celebrating the state visit. The Pope told those gathered that without prayer the world was "filled with a growing noise and confusion, filled with false paths leading only to heartbreak and illusion".