Pope's UK visit proving controversialSTORY HIGHLIGHTS- NEW: Benedict speaks at Westminster Hall on Friday
- Pope: The church has not been vigilant or fast enough to respond to sexual abuse
- The pope is visiting England and Scotland for four days
London, England (CNN) -- Pope Benedict XVI will make a speech at London's historic Westminster Hall on Friday, where he is expected to talk about the positive contributions Catholics have made to society.
He will also lead prayers with the head of the Church of England, Archbishop of Canterbury Rowan Williams.
The address by the pontiff comes a day after he said the Roman Catholic Church has not been vigilant enough or fast enough in responding to the problem of sexual abuse by priests.
"These revelations were for me a shock and a great sadness. It is difficult to understand how this perversion of the priestly ministry was possible," he told reporters aboard his plane to Scotland. "How a man who has done this and said this can fall into this perversion is difficult to understand."
He added, "It is also a great sadness that the authorities of the church were not sufficiently vigilant and insufficiently quick and decisive in taking the necessary measures."
British people feel overwhelmingly that the pope has not done enough to punish priests who abuse children, according to a ComRes poll for CNN released as Benedict arrived in the country. Three out of four British people -- and two out of three Catholics in the country -- say he should do more to punish abusive clergy.
RELATED TOPICS- Pope Benedict XVI
- The Roman Catholic Church
The pope is in London on the second day of a historic four-day state visit to Britain, where the issue of abuse, and the Vatican's perceived lack of response to it, has created anger.
But there was a warm welcome for him on a cold afternoon in Glasgow, Scotland, for the first major mass of his visit.
Tens of thousands turned out to hear him preach, with members of the faithful describing it as a "happy day" and calling it a "great honor" that he had come.
Benedict elaborated in Glasgow on what's expected to be a major theme of his visit, the value of religion in a society that he sees as increasingly secular.
"There are some who now seek to exclude religious belief from public discourse, to privatize it or even to paint it as a threat to equality and liberty," he said in his homily. "Yet religion is in fact a guarantee of authentic liberty and respect."
He also urged bishops to look after their priests -- possibly an oblique reference to the sex abuse scandal -- and warned young people against the temptations of "drugs, money, sex, pornography, alcohol -- which the world tells you will bring you happiness, yet these things are destructive and divisive."
Benedict started his visit in Edinburgh, where he held a meeting with the queen and greeted thousands who turned out to see him on the streets of the Scottish city.
Though a pope has visited Britain once before -- Pope John Paul II in 1982 -- this is considered the first state visit by a pope to Britain because it comes at the invitation of the queen, not the Catholic Church, as was the case 28 years ago.
Benedict's trip is scheduled to include meetings with political leaders, royalty, and bridge-building events with Anglican Church officials. It will culminate in the beatification of British Cardinal John Henry Newman, a Catholic convert who died in 1890 and is credited with helping rebuild Britain's Catholic community.
There has been widespread outcry over the estimated 12 million pounds ($18.7 million) British taxpayers are having to pay for the visit, though Christopher Patten, the prime minister's representative for the papal visit, has pointed out that one day of last year's G-20 summit in London cost 20 million pounds.
Criticism has also focused on the armed police squads needed to protect a religious figurehead previously targeted by attackers.
Along with anger about the Vatican's response to child and sexual abuse, there is criticism over the pope being granted a state visit, given the Catholic Church's attitudes towards gender equality and homosexuality.
Catholic leaders and government officials have defended the trip, with Prime Minister David Cameron saying Britain and the Vatican have "incredibly important work to do together" in promoting a "multi-faith dialogue."
CNN's Phil Black and Erin McLaughlin contributed to this report.