Archbishop Georg Gaenswein, an aide to both retired Pope Benedict XVI and Pope Francis, told a book presentation that he by no means was comparing the scandal to the nearly 3,000 people killed in the US on September 11 2001.
But he said the years-long sex scandal, and recent revelations in a Pennsylvania grand jury report, showed "how many souls have been wounded irrevocably and mortally by priests from the Catholic Church".
"Today, even the Catholic Church looks full of confusion at its own 9/11, at its own September 11, even though this catastrophe isn't associated with a single date but rather at so many days and years, and innumerable victims," he said.
While no one has attacked churches with planes full of passengers, Mr Gaenswein said, recent news from the US "sends a message that is even more terrible than the sudden collapse of all the churches of Pennsylvania together with the Basilica of the National Shrine of the Immaculate Conception in Washington".
Mr Gaenswein, who serves as secretary to Benedict and prefect of Francis's papal household, was speaking at a presentation of a book by conservative American author Rod Dreher, who has been at the forefront in reporting on the recent scandal in the US over ex-Cardinal Theodore McCarrick.
Francis removed McCarrick as a cardinal in July following a credible accusation that he groped a teenage altar boy in the 1970s. Soon after it emerged that it was apparently an open secret - including at the Vatican - that McCarrick routinely bedded seminarians and young priests.
The McCarrick scandal has taken on crisis proportions after the Vatican's former US ambassador, Archbishop Carlo Maria Vigano, accused two dozen Vatican and US cardinals and bishops of covering up for McCarrick for two decades.
Specifically, Mr Vigano accused Francis of rehabilitating McCarrick from canonical sanctions imposed on him by Benedict 2009 or 2010.
The Vatican has not responded to the accusations, but "clarifications" are expected.
Mr Gaenswein, who serves as an occasional spokesman for Benedict, has limited his comments about the scandal to denying a report that Benedict had confirmed Mr Vigano's 11-page denunciation.
Mr Gaenswein did not refer to the Vigano scandal on Tuesday, but more generally to the "turbine of news of recent weeks". He cited specifically the Pennsylvania grand jury report, which found 300 priests abused more than 1,000 children over 70 years - and bishops covered up for them.
Stay up to date with the latest news stories from a Christian perspective. Sign up to our daily newsletter and receive more stories like this straight to your inbox every morning.
