Italy's interior minister has accused Roman Catholic bishops of trying to weaken the government by opposing new rights for unmarried and gay couples.
The divisive issue has seen pro-gay campaigners take to the streets
Giuliano Amato said the Church was meddling when it issued a directive at a bishops' conference calling a new bill "unacceptable and dangerous".
Recent polls show most of Italy's Catholics are in favour of changes to the law, despite Church opposition.
About 500,000 unmarried Italian couples are without shared rights or benefits.
They miss out on social benefits, property or inheritance, a situation that is now at odds with many countries in Europe.
When Prime Minister Romano Prodi came to power last year he promised his supporters that the government would bring in new laws to protect cohabiting couples.
But with only a razor-thin majority in the Senate, Mr Prodi needs the full support of all sides of his coalition, including the Catholic MPs in the centre, and that looks increasingly unlikely, says the BBC's Rome correspondent Christian Fraser.
A defeat on this controversial bill will divide his coalition and could ultimately lead to the collapse of the government, our correspondent says.
Mr Amato spoke out after the Italian bishops' conference issued a statement saying that legal recognition of unwed couples was "unacceptable as a principle and dangerous on a social and educational level".
Legalising unions between people of the same sex, it added, was an even more serious problem.
"This is something that happens in societies we criticise as Islamised," Mr Amato said.
He was supported by Piero Fassino, the leader of Italy's largest left-wing party, the Democratic Left.
But Catholics on both sides of the political divide applauded the bishops' statement.
Opposition leader Silvio Berlusconi said the Church had a right to speak out on the issue.
Justice Minister Clemente Mastella who leads a Catholic party in Mr Prodi's coalition, said: "Now we are not alone."
Recent polls showed that most Catholics in Italy are in favour of changes to the legislation despite Church opposition.