Hundreds of thousands of demonstrators are expected to turn out in support of 'traditional family' in Italy on Saturday as the government debates legalising same-sex partnerships.

A week after pro-gay demonstrators took to the streets in Rome, Catholic leaders in Italy have organised a "Family Day" for those opposed to the legislation to gather at Circus Maximum in the capital.

The government will begin debating civil partnerships later this week. There are indications however that the legislation could fail in the upper chamber, where it will be voted on by secret ballot. Italy is the only country remaining in Europe to recognise neither civil partnerships nor gay marriage. In the UK, England, Wales and Scotland recognise both. Northern Ireland recognises civil partnerships but not gay marrige. The Republic of Ireland voted in favour of gay marriage last November.

Defending the importance of the traditional family model, Cardinal Angelo Bangasco, president of Italy's Bishops' Conference, said the family is a "treasure chest of relationships, generations and genres, of humanism and of grace" in which children are the "jewel in the crown".

He said their welfare must prevail over all else, as they are the weakest and most exposed. Echoing words of Pope Francis, he said children needed a father and a mother. "The family is an anthropological fact, not ideological."

He also defended the right of Christians to have their voice heard. "Believers have the duty and the right to participate in the common good with serenity of heart and constructive spirit." He urged the laity of the secular world "to include the divine law in the life of the earthly city" and shoulder their responsibilities in the light of Christian wisdom and "with eager attention" to the teaching of the Church. 

He said: "We must never forget the identity of the family and its importance for stability and economic development of the country, as well as the essential role played by the education of future generations."

Earlier this month a poll in Italy showed 46 per cent in favour of civil unions for same-sex couples and 40 per cent against. However, more than half, 55 per cent, opposed same-sex marriage and just 38 per cent were in favour. More than eight in ten opposed adoption by same-sex couples.