BERLIN—The sexual-abuse scandal roiling the Roman Catholic Church is threatening one of the pope's core missions, a Christian reawakening in Europe.

Pope Benedict XVI has made reversing the decline of Catholic influence in Europe a central goal of his papacy. But as clerical abuse scandals spread across the Continent, they threaten to hasten a growing movement away from the Catholic Church in an increasingly secular Europe.

A survey published last week in the German magazine Focus underscores that threat. Some 56% of 613 Germans polled by researchers at Zeppelin University in Friedrichshafen, Germany, said they had no confidence in the church; one-quarter of the survey's Catholic respondents said they were mulling leaving the church.

"This is a real danger for Benedict," said David Gibson, author of "The Rule of Benedict," a biography of the pope. With alienation hitting the very places that could be the seedbeds for the pope's push, Mr. Gibson said, "his great project could be cut off at the roots."

On Monday, Pope Benedict marked the fifth anniversary of his papacy by lunching with cardinals in the frescoed interiors of the papal palace. Also on Monday, the Vatican published a letter from Cardinal Claudio Hummes, head of the Vatican's Congregation for the Clergy, to priests world-wide noting that the church "is determined to neither hide nor minimize" sexual-abuse. Sexually abusive priests, the cardinal wrote in a letter dated April 12, "must answer for their actions before God and before tribunals, including the civil courts."

It was just five years ago this month that a freshly elected Pope Benedict explained before thousands of pilgrims gathered in Rome's St. Peter's Square the inspiration for his papal name: One was Benedict XV, the pontiff who guided the church through the turbulence of World War I.

The other was St. Benedict of Norcia, a sixth-century monk who, amid the ashes of the Roman Empire, retreated to the hills south of Rome to found a monastic movement that would become the bedrock of European Christian culture in the centuries to follow. His namesake, the pope declared, "is a powerful call to the irrefutable Christian roots of European culture and civilization."

That history has blurred the lines between church and state across much of Europe. Many countries, such as Germany, Austria, Italy and Sweden, collect some form of a church tax that provides the lion's share of Catholic and Protestant churches' finances.

Even countries with small Protestant or Catholic church attendance, such as Denmark and the Netherlands, observe Good Friday, Ascension Day and Pentecost as public holidays. Germany and Italy are currently governed by church-friendly center-right coalitions.

Yet in daily life, Europe has become increasingly irreligious, a shift rooted in part in its post-war prosperity and the growing chasm between European social mores and the church's moral teachings on issues such as contraceptives, divorce and homosexuality.

Even before recent months' clerical abuse allegations, church attendance in Europe was at historical lows. In Spain, a traditional Catholic stronghold, fewer than 20% of Spaniards attend mass regularly, down from more than 30% in the 1980s, according to a 2008 nationwide study. In Germany, fewer than 14% of Catholics attend church regularly, compared with 29% three decades ago. In the U.S., by comparison, some 42% of Catholics and 47% of Protestants say they attend church regularly, according to Gallup Poll data.

Between 2000 and 2008, the number of priests in Europe declined about 8%, based on the most recent Vatican figures. The church's aging clergy signals a more precipitous drop ahead: In Ireland, for instance, 36% of its priests are over the age of 65, while only 4% are 34 or younger.

The abuse scandals have further undermined the church's influence. In Munich, for example, home to some 540,000 Catholics, city officials say 1,691 people, most of them Catholic, left the church in March alone, more than double last year's monthly average.

Lars Frantzen of Cologne, Germany, a 34-year-old computer scientist who was brought up in a conservative Catholic family, says he considers himself religious. But over the years, he says, he found himself increasingly at odds with the church's message and remoteness from the issues of his own life. "There isn't the will to engage people," he said. "It seems more to want to control people." The recent abuse revelations, he said, were the final straw. "What's happened in the church is the opposite of what the church should stand for," said Mr. Frantzen, who left the church in February.

Benedict's approach to reinvigorating the church has been less about broadening its appeal among the less ardent multitudes and more focused on cultivating a core of traditional believers in church doctrine. Last fall, the Vatican stepped up its courtship of traditionalist Anglicans uneasy with their church's female priests and openly gay bishops.

Some Church observers say the scandals ultimately could lead to reform and renewal within the church, given that surveys consistently show the majority of Europeans say they still identify with Christian messages and values.

"But that requires a thorough reflection on the church's part on how it transitions into modernity," said Peter Huenermann, retired professor of theology at the University of Tübingen in Germany, where Pope Benedict, then Joseph Ratzinger, taught theology during the 1960s. "I don't know if the pontiff has the will to carry out such a change."

Others point to the growing popularity of charismatic churches and pilgrimages as evidence of the role religion continues to play in Europe. Thousands of tourists and pilgrims have flocked to northern Italy to see the Shroud of Turin, the ancient piece of linen some believe was Jesus Christ's burial cloth, since it went on display earlier this month. "There's no reason the Catholic Church can't take part in" such a revival, said Grace Davie, professor of sociology at the University of Exeter in the U.K.
—Stacy Meichtry contributed to this article.