Pope Benedict XVI today spoke of the "shame and humiliation" brought by child abuse allegations against the Catholic Church.
Speaking during a televised service at London's Westminster Cathedral, he acknowledged the "immense suffering" inflicted by ministers. "I think of the immense suffering caused by the abuse of children, especially within the church and by her ministers," the Pope said.
"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.
The vigil will be the climax of the third day of the Pontiff's historic visit.
Benedict XVI's itinerary has not changed as a result of a police investigation which resulted in six arrests on Friday and this morning is meeting the British prime minister David Cameron
Mr Cameron missed the Pope's address to MPs in Parliament's Westminster Hall on Friday because he was attending the funeral of his father, Ian, who died last week.
The Pope will greet Mr Cameron at Archbishop's House, in central London, before welcoming Deputy Prime Minister Nick Clegg and then Harriet Harman, the acting leader of the Opposition.
He will attend Mass at Westminster Cathedral at 10am.
Spectators will be able to catch a glimpse of the Pontiff as he travels by Popemobile along Horse Guards Road, The Mall, Constitution Hill and Hyde Park Corner from 6pm on his way to the Hyde Park prayer vigil.
It is intended as a celebration of the vitality of the Catholic Church in England and Wales and will include music, readings and drama as well as prayer and contemplation.
The event will be compered by television presenter Carol Vorderman and writer Frank Cottrell-Boyce and teenage Britain's Got Talent star Liam McNally will sing.
Representatives from every Catholic diocese in England, Scotland and Wales will take part in a procession.
Speakers will include Barry and Margaret Mizen, the parents of murdered schoolboy Jimmy Mizen, who will talk about their son's death and how their faith has helped them through the past two years.
The couple said it was "a privilege" to be asked to take part.
During his visit, the Pope has warned of the faith's "increasing marginalisation" and repeatedly argued religion should be recognised for its "vital" contribution to the nation.
Last night Pope Benedict expressed fears for the future of religion as his historic visit to Britain continued despite six arrests over an alleged plot against him.
On a day that saw him make first visits by a pontiff to Lambeth Palace and Westminster Abbey, the pontiff expressed concerns “at the increasing marginalistion of religion, particularly of Christianity” and pointed to “worrying signs” that believers’ rights to freedom of religion and of conscience were under threat.
In a powerful address last night to leaders of British society at Westminster Abbey, where he took part in an ecumenical celebration, Pope Benedict said: “There are those who would advocate that the voice of religion be silenced, or at least relegated to the purely private sphere.
“There are those who argue that the public celebration of festivals such as Christmas should be discouraged, in the questionable belief that it might somehow offend those of other religions or none.
“And there are those who argue – paradoxically with the intention of eliminating discrimination – that Christians in public roles should be required at times to act against their conscience and freedom of religion.”
He also told his audience – who included former British prime ministers Gordon Brown, Tony Blair, John Major and Margaret Thatcher – that moral failure was to blame for the global crisis.
As crowds of the faithful – and protesters – thronged the streets of Westminster, the pontiff called for a strong role for religion in politics. Religion, he argued, should be recognised for its “vital” contribution to the nation.
Earlier, at a meeting with Archbishop of Canterbury Rowan Williams, the pope gave thanks for “the remarkable progress” made in ecumenical relations in recent decades. But he continued, “we recognise that the church is called to be inclusive, yet never at the expense of Christian truth”.
Later at Westminster Abbey, he acknowledged the progress made on the ecumenical journey but said, “We must also recognise the challenges which confront us, not only on the path to Christian unity, but also in our task of proclaiming Christ in our day.”
The pope began the day with a reference to the child abuse scandal, saying schools must provide a “safe environment” for children. Speaking to religious leaders in St Mary’s College Twickenham, he said: “I wish to add a particular word of appreciation for those whose task it is to ensure that our schools provide a safe environment for children and young people. Our responsibility towards those entrusted to us for their Christian formation demands nothing less.”
Last night the National Secular Society, which has strongly opposed the state visit and the pope’s handling of child sex abuse cases and his views on homosexuality and other issues, called on protesters to join a march taking place near Hyde Park this afternoon.
The call came as six north African men, five employed as London street-cleaners, were being questioned by police last night under anti-terrorism legislation, following a dawn raid by armed officers. So far, however, nothing has been found to show they were involved in any plot to harm the pope, though police acted on information received late on Thursday night.
Security remained tight for the visit, but no changes were made to the pope’s plans for his busy day of engagements.