It means that for the first time in Germany, more Catholics abandoned their church than Protestants.
A survey by magazine Christ & Welt, a lift-out carried by weekly Die Zeit, revealed that 180,000 Catholics left the church in 2010, which was a rise of 40 percent on the previous year.
That compared with 150,000 leaving the country's Protestant Church (EKD).
Membership decline was concentrated in the first half of the year, when public anger over child abuse scandals was at its peak, the magazine reported.
Many Catholics had left as a “personal form of protest and expression of disgust,” Cologne vicar-general Dominik Schwaderlapp told Christ & Welt.
The magazine surveyed 27 Catholic dioceses, 24 of which provided definite figures or estimates.
Especially hard hit were the Bavarian dioceses of Augsburg, Bamberg, Eichstätt, Passau and Würzburg, where the number of people leaving the church climbed by as much as 70 percent on the previous year.
Augsburg was the diocese of controversial bishop Walter Mixa, who stepped down a year ago amid allegations that he beat children while he was head of the Schrobenhausen children's home in Bavaria, as well as claims of sexual abuse and alcoholism.
This followed months of revelations about sexual and physical abuse within the church, starting in January 2010 when it emerged that priests at the elite Canisius College in Berlin committed dozens of assaults on pupils in the 1970s and 1980s.
More than 200 cases of such abuse at church institutions throughout the country emerged in the months that followed.
The dioceses of Trier and Rottenburg-Stuttgart, which are regarded as liberal within the church, also suffered more than 60 percent rises in the number of members quitting. The archdiocese of Cologne saw a 41 percent rise.
The Berlin and Hamburg archdiocese each suffered a relatively mild exodus, with the numbers leaving rising by less than 20 percent.