The Vatican has lodged an “unprecedented” interference in Italian politics by objecting to a law that would criminalise violence and hate speech against gay and transgender people.

The Holy See confirmed on Tuesday that it had sent a diplomatic protest to the government of prime minister Mario Draghi over the so-called Zan bill, which would punish acts of discrimination and incitement to violence against gay, lesbian, transgender and disabled people.

The bill, promoted by Alessandro Zan, a gay MP from the centre-Left Democratic Party, was approved by the lower house of parliament in November.

It is now going through the Senate, where it faces stiff resistance from hard-Right politicians such as Matteo Salvini, the head of the League, and Giorgia Meloni, the up-and-coming leader of Brothers of Italy, heirs to Italy’s Fascist movement.

The Italian bill is being pushed by Alessandro Zan, an MP with the centre-Left Democratic Party

Credit: AP

Conservatives and some Catholics argue that the bill would be an attack on freedom of expression and that it is unnecessary because existing laws already condemn homophobia.

The Vatican is worried that the passing of the law could lead to the Catholic Church in Italy being prosecuted for refusing to conduct gay marriages, for opposing adoption by gay couples through Catholic institutions or for refusing to teach gender theory in Catholic schools.

But its decision to lodge a formal protest with Italy, a separate sovereign state, was described by atheist groups and LGBT associations, as well as the Italian press, as “unprecedented”.

The protest was sent last week by a British archbishop, Paul Gallagher, who as Secretary for Relations with States is effectively the Vatican’s foreign minister.

As Secretary for Relations with States, British archbishop Paul Gallagher is the Vatican's de facto foreign minister

Credit: AFP

The Vatican argues that the Zan bill violates the Concordat, part of the Lateran Pacts that have since 1929 governed relations Rome and the Holy See.

The proposed law would jeopardise the “liberty” that was guaranteed by the treaty to the Catholic Church in Italy, the diplomatic note said.

The Italian Bishops Conference has already protested against the bill, saying that a “law intended to fight discrimination must not pursue that objective with intolerance.”

The bill would “put at risk” fundamental principles such as freedom of thought and speech, Cesare Mirabelli, a former president of Italy’s constitutional court, told Vatican News, the Vatican’s news outlet.

But Mr Zan, the MP pushing the bill, said the Vatican’s concerns were unfounded. “The bill does not restrict in any way freedom of expression or religious freedom,” he wrote on Twitter.

“All the concerns and doubts will be listened to, but there cannot be any foreign interference in the workings of a sovereign parliament.”