Church heads not vigilant over sex abuse: Pope

Pope Benedict criticised Catholic church leaders on Thursday as "insufficiently vigilant" during decades of sexual abuse of children as he arrived in Britain to win over one of Europe's most secular countries.

The German pope was greeted by Queen Elizabeth at the start of his four-day visit, which comes at a time when the Catholic church is struggling with a global child sex-abuse scandal.

In some of his clearest remarks on the scandal, he told reporters aboard the plane taking him to Scotland that he was shocked by the revelations.

"It is difficult to understand how this perversion of the priestly ministry was possible," he said.

"It is also a great sadness that the authority of the church was not sufficiently vigilant and not sufficiently quick and decisive in taking the necessary measures."

Benedict has a delicate path to tread in England and Scotland in relations with the Anglican church after his offer last October making it easier for disaffected Anglicans, unhappy over the ordination of women and gay bishops, to convert.

He told reporters it was not the mission of the Catholic Church to change with the times "to try to be more attractive", but to declare what it believed to be fundamental truths.

The Queen, after holding talks with the pope at her official residence in Scotland, spoke of the common Christian heritage that Anglicans and Catholics shared, and of their common belief that religion should never be allowed to justify violence.

"We know from experience that, through committed dialogue, old suspicions can be transcended and a greater mutual trust established," she said in a welcome speech.

The pope told reporters he was not concerned by the prospect of protests against his visit, saying he was certain that Britain''s sense of "respect and tolerance" would prevail.

The Vatican played down comments by Cardinal Walter Kasper to a German magazine, in which he compared England to a Third World country and suggested it was home to aggressive atheism.

Kasper, who recently retired as head of the Congregation for Christian Unity, the Vatican department that oversees dialogue with Anglicans, had been due to accompany the pope but a Vatican spokesman said he would miss the visit for health reasons.

The pope paraded through Edinburgh enclosed in the glass of his "popemobile", and was due to preside at an open-air mass in nearby Glasgow in the afternoon.

Thousands of seats remained unclaimed, and police suggested the park venue could be one-third empty.

Local Catholics, while acknowledging Benedict lacks the charisma of his predecessor John Paul II, who attracted hundreds of thousands during a visit in 1982, remain positive about the trip.

"I think it's a privilege that the Pope is in Scotland," said Teresia McFarlene, 65, a former window dresser waiting in Edinburgh for the pope's convoy to drive past.

A group of about 150 protesters gathered on the route, waving gay rainbow flags, shouting through a megaphone and even blowing on a South-African-style vuvuzela horn.

One banner read "Pope opposition to condoms kills people", and another: "Stop protecting paedophile priests."