Throw a coin over your shoulder into Rome's Trevi Fountain, the legend says, and it will bring you good fortune and you will one day return to the Eternal City.

It is an essential tradition for millions of tourists. But few will have suspected their loose change would also spark a bitter row between Rome's secular authorities and the Catholic Church.

Traditionally, the €1.5 million (£1.3 million) of coins scooped out of the stunning Baroque fountain each year are actually destined for the Catholic charity, Caritas, to help the city’s poor and homeless.

Now Rome’s Mayor, Virginia Raggi, says the €4,000 (£3,600) worth of coins tossed into the fountain every day belong to her administration.

From April 1 the donations will no longer be paid to Caritas, but are to be used by Rome City Council for the maintenance of cultural sites and social welfare projects.

The proposed changes, reportedly approved by the council at the end of December, have provoked a backlash from the Catholic Church.

Avvenire, the daily paper produced by the Italian Bishops Conference, launched a scathing attack on the council in its Saturday edition, describing the city’s bureaucracy as “the enemy of the poor” in a front-page article headlined “money taken from the poorest”.