Researchers say more than half of Catholic priests have reported significant rise in attendance since election of new pontiff

Hundreds of thousands of Italian Catholics have flocked back to church since the election of the pope, according to a study published on Mondaythat credits the "Francis effect" for the boost in congregations.

Researcher Massimo Introvigne, a sociologist and head of Italy's Centre for the Study of New Religions (Cesnur), found that 51% of 250 priests he interviewed reported a significant rise in church attendance since the election of the former Cardinal Jorge Bergoglio in March.

"If we project those results nationally, and if only half the parishes and communities in Italy have been touched by the Francis effect, then we're talking about hundreds of thousands of people who are returning," he said.

There was evidence that the 76-year-old Argentinian pope had made an even more dramatic impact in Britain. In a smaller survey, of 22 British cathedrals, 65% of the respondents had said they had noticed a rise in numbers, Introvigne added.

He said he first discovered evidence of a surge in attendance at mass in a survey he carried out soon after Francis became pope. He decided to conduct a more extensive poll to see if observance had since returned to its previous level.

"It might have been attributable to the novelty of having a new pope and the emotions stirred by the resignation of pope Benedict. But after six months I got more or less the same result," he said.

According to two of Italy's most senior clerics, Francis is making his biggest impact on long-lapsed Catholics. Cardinal Giuseppe Betori, the archbishop of Florence, said: "So many are returning to the sacraments, in some cases after decades."

His account was borne out by the auxiliary bishop of L'Aquila, Giovanni D'Ercole, who said in an interview with the daily La Stampa that "Francis makes headway above all among those who had distanced themselves from Christian life."

Introvigne cautioned that the persistence of the Francis effect would depend on how parish priests dealt with those who had previously abandoned their faith: "whether they are made to feel welcome" and whether they were given a proper re-introduction to Catholicism.

Pope Francis, who was noted for his simple lifestyle while archbishop of Buenos Aires, has refused the opulent trappings of the papacy and repeatedly advocated a simpler, poorer and less bureaucratic church. Some of his initiatives have also suggested he intends decentralising the administration of the world's biggest Christian denomination.

In one of the first public signs of misgivings, an influential Catholic writer on Sunday disparaged the idea of a less hierarchical church and defended the Vatican bureaucracy. Vittorio Messori, whose book-length interview with the late pope John Paul II sold millions of copies around the world, wrote in the daily Corriere della Sera that the dream of a "poor, egalitarian church [reminiscent of its] origins in which faith is freed of superstructures" was at odds with the historical fact that charismatic movements that "refused to change into hierarchical institutions" were swiftly reduced to irrelevance.