"This phenomenon is nothing new in France," Father Michel Le Long told IslamOnline.net on Saturday, August 18, on the sidelines of a Church-sponsored forum on Islam in France.
"It has everything to do with the historical conflict between the state and the church, which left the church almost powerless and marginalized.
Le Long also faulted the secular nature of French society for the religious gap.
"Under this secular system, religion, in general, and Christianity, in particular, have become increasingly sidelined and toothless," he added.
Nearly 40 Catholic bishops from across France are attending the week-long forum, which kicked off Monday, August 13, to seek an in-depth knowledge of Islam and its teachings.
"The issue dominating the forum's agenda is that why mosques are always complete while churches deserted even on Sundays," Christophe Ricco, the French Catholic Church's head of Muslim-Christian Dialogue Department, told Le Monde.
France is home to around six million Muslims, the largest Muslim minority in Europe.
According to the CIA World Fact Book, Roman Catholics constitute between 83-88 percent of the French population followed by Muslims between 5-10 percent, Protestants two percent and Jews one percent.
Bishops attending the forum further said even a large portion of Muslims of the second and third generations, who were born in France and absorbed its secular system, are punctual mosque-goers.
"Most of them don't even master Arabic," said bishop Philippe. "It is an unprecedented phenomenon in French history."
"More and more, reversion to Islam is also a fact in France."
French estimates show that 50,000 French have reverted to Islam in France.
Muslims have around 1,500 prayer areas, most of which are housed in small, modest halls, often described as "basement mosques."
They complain that such rooms are too small for their congregations.
"We perform the weekly Friday prayers on the street as there is no space for worshippers inside the mosque," said Mamdou Brahim of the Fath Mosque in Paris.
"This has prompted complaints from shop owners and locals," he added.
Though Islam is the continent's second religion, Muslims across Europe are facing campaigns from far-right groups and some church leaders to have stately mosques.
In France, the far-right political party National Republican Movement (MNR) won two court cases this year against giving pieces of land at low prices to Muslims to build two grand mosques in suburbs of Montreuil and in Marseille, both having a sizable Muslim minority.