The fate of Romano Prodi’s administration rests on the votes of Senators after one of the nine parties that form the coalition government withdrew.

Yesterday he called on Parliament to back him after the Christian Democrats pulled out on Monday, leaving him two votes short of a Senate majority. He has been in government less than two years.

The House of Deputies, where he retains a majority, will vote on a motion of no confidence today.

Christian Democrat leader Clemente Mastella resigned as Justice minister last week after his wife was embroiled in a corruption scandal.

He complained that his coalition partners had been insufficiently supportive and that the corruption investigation is retaliation for his attempts to reform the judiciary.

The nature of the Italian political system means that since 1945 the country has mostly been ruled by fragile coalitions, and the group of parties that finally removed Silvio Berlusconi from office in April 2006 are no different.

Mr Prodi’s commitment to increased gay rights has caused tension in the coalition.

Proposals from ministers to bring forward a draft bill that would grant any unwed couple, gay or straight, the right to register themselves as a family have stalled.

Last year the former Justice minister claimed he would rather the government fall than pass this law.

“Homosexuals can acquire more rights but I’ll never accept the idea that they can be considered a family,” Mr Mastella said.

The proposed new law would also grant some pension and health insurance rights, but falls far short of the civil partnerships gay and lesbians in the UK enjoy.

Italy is perhaps the only country in Europe where the Roman Catholic church retains such strong influence over politics.

Church-state relations remain frosty following Pope Benedict XVI’s repeated attacks on the proposed legislation to recognise gay couples.

The secretary general of the Italian bishops’ conference has accused the government was trying to “unhinge” the traditional family.

Leftist members of the government, however, are determined to advance gay rights – if the coalition can be held together.