Gianfranco Formenton, a priest in Italy’s central Umbria region who has long preached against racism and in support of migrants, knows what it is like to clash with Matteo Salvini, the recently installed interior minister and leader of the far-right League party.

In response to the party’s xenophobic rhetoric in 2015 – the year more than a million migrants arrived in Europe and 150,000 landed on Italy’s southern shores – he put a sign up on the door of his church in San Martino di Trignano, a hamlet of the town of Spoleto, saying: “Racists are forbidden from entering. Go home!”

He immediately bore the wrath of Salvini, who wrote on Twitter: “Perhaps the priest prefers smugglers, slaveholders and terrorists? Pity Spoleto and this church if this man [calls himself] a priest.”

Fr Formenton is also believed to have been the target of intimidation by far-right sympathisers when his rectory and home were ransacked a few days after Luca Traini, a failed League candidate in a local ballot, injured six Africans in a shooting in the town of Macerata in early February.

As the Democratic party, the biggest left-wing force in Italy, appears cowed in the face of Salvini’s vitriolic immigration stance, fearing it will lose support, the interior minister’s strongest opponents are priests such as Formenton.

But they are struggling to convince parishioners to welcome migrants, amid mounting adulation of Salvini, a Catholic who reportedly attends mass.

“We have a population that wants blessings from the church, processions and religious rites, but every time Pope Francis recalls migrants or the poor, they no longer listen,” Formenton told the Guardian.

“There is an evil force of racism, and Salvini has contributed to this. He’s been a magician in cultivating hate and manipulating anger. People of all ages have become racist because of the climate we’re living in.”

Knowing that many of his backers are devout Catholics, Salvini has exploited religion to galvanise support. The 45-year-old once again brandished a rosary and swore on the gospel to be “loyal to his people” while addressing thousands of ecstatic voters at the League’s annual rally in Pontida, a town in the northern Lombardy region, last Sunday. His speech, during which he pledged to create a European-wide alliance against “mass immigration”, came a few days after Mario Delpini, the Archbishop of Milan, pleaded for more humanity among Christians.

“Can they go to mass each Sunday and ignore the drama that is happening in front of their eyes?” said Delpini.

In the few days since Salvini’s speech, more than 200 migrants have drowned in the Mediterranean.

Pope Francis also spoke out after Salvini, who is also deputy prime minister, blocked the Aquarius, a rescue ship with more than 600 people on board, from docking in Italy in June. “I encourage those who bring them aid and hope that the international community will act in a united and efficient fashion to prevent the causes of forced migration,” the pontiff said.

At the same time, Salvini has been nurturing a relationship with US Cardinal Richard Burke, a fierce critic of Pope Francis and supporter of Donald Trump, as he strives to build consensus from within the church.

Cosimo Scordato, a priest at Saint Francesco church in Ballarò, a neighbourhood of Palermo and home to many migrants recently arrived in Sicily, compared Salvini’s use of religious imagery to that deployed by Mafia bosses.

“Holding a rosary in front of thousands of supporters reminds me of Mafia bosses holding the Bible,” Fr Scordato, who has been subjected to intimidation by the Mafia, told the Guardian.

“Mobsters believe themselves to be sort-of spokesmen of Christian values, they feel protected by the church and want to show people they have God on their side.”

Scordato said he recently wrote a letter to Salvini encouraging him to see migrants as an opportunity in a country with a low birth rate and ageing population. He got no reply.

Fr Enzo Volpe, a Salesian priest in Palermo, said Christians have “forgotten about the Good Samaritan, who healed and took care of the poor”.

“Young Italians are moving to the US and England in search of work and opportunities,” he added. “What if these countries had stopped Italians at the border like Italy is doing with Africans? What’s the difference? Is it because Africans are black?”

Fr Luigi Ciotti, one of the most popular priests in Italy, organised a protest this weekend, which invites people to wear a red T-shirt – the same colour worn by three-year-old Syrian Aylan Kurdi when his drowned body washed up on a beach in Turkey in 2015.

“Red also means to stop,” he said. “And we need to stop now, stop and reflect and look inside ourselves. We need to question our hearts and conscience: what are we becoming?”

Earlier this week Fr Alex Zanotelli, a member of the Comboni missionaries in Verona, urged journalists to report on the tragedies in Africa and raise more awareness among Italians about the plight of migrants, who are now perceived by many as “parasites” and “invaders”.

“If Italians don’t know what’s going on in Africa, they cannot understand why so many people are fleeing their lands and risking their lives,” he said.

But with the Democratic party failing to voice a strong opposition, the onus rests on the priests to wrestle against Salvini.

“The party is divided and doesn’t know how to counteract Salvini, and on which issues,” said Mattia Diletti, a politics professor at Sapienza University in Rome. “Due to people being so connected to him and the immigration issue, there is a fear that [opposing him] could be damaging.”