The report said only half of all Belgians still identify as Catholics, compared to 72 per cent three decades ago, and 42 per cent now said they are atheists or agnostics.
Fewer than five percent of Belgian Catholics attended Sunday Mass in 2009, compared to 29 per cent in 1977.
Only about one-quarter of couples marry in church now, a steep drop from 78 per cent in 1977, and infant baptisms have dropped to 55 per cent from 85 per cent, the report said.