The Catholic Church moved closer to a split over homosexuality and marriage after divorce today after traditionalists called for a walk out by "faithful" bishops at the Synod on the Family in Rome.

The Twitter hashtag #synodwalkout quickly began trending after the conservative blog One Peter Five set up a change.org petition calling on the conservative cardinals and archbishops to stage a walkout. Within hours of being posted early this morning, the petition gained more than 1,600 signatures.

Observers in Rome and on social media began talking of "chaos", and headlines such as "showdown in Rome" began to appear on well-informed conservative websites.

Catholic blogger Joe Sales tweeted:

One Peter Five reports: "As the evidence mounts that the Synod's outcome has been pre-determined, I have joined a number of other concerned Catholics in writing an open letter. In it, we request that those Synod fathers who are faithful to Christ's teachings, if they continue to be thwarted in their efforts, walk out of the Synod before it is over rather than allow their participation be interpreted as support."

The conservative blogger adds: "Even at this late hour, we must try to protect the faith."

The petition urges:

"We thank you for your witness to and defence of the truth of Matrimony and Family proclaimed by the Church, in fidelity to our Lord Jesus Christ. As the Ordinary Synod on the Family continues its work, confusion and scandal spread among the faithful. Catholics are concerned that some members of this body of apostolic successors, under the guidance of the Pope, are seeking to endorse homosexual relationships, effectively question the indissolubility of marriage, and permit the distribution of the Holy Eucharist to the unrepentant."

The last sentence refers to the argument put forward by some German bishops and others that people who have had a civil remarriage after a divorce should no longer be barred from Holy Communion and other sacraments. Many people believe this ruling is cruel and inhumane and causes unnecessary suffering among innocent victims of adultery and betrayal. But conservatives believe it must be enforced rigidly because they believe it represents faithfully what Jesus taught about the indissolubility of marriage.

The petition says the Synod's working document is "unacceptable from an orthodox Catholic point of view" regarding divorce and attempted remarriage, homosexuality, and contraception and describes "profound sorrow" at the ongoing development of the crisis.

The petition warns: "We fear, evidenced by all of the above, that the Ordinary Synod will attempt to recommend changes in teaching and pastoral practice that are contrary to the Gospel of Christ and the constant teaching of the Church on the sacred mystery of Catholic marriage and the nature of human sexuality. This would pose a clear and present danger to souls."

The petition came as Italian papers are reporting that opponents of attempts to liberalise the Church are throwing "poisoned meatballs" in a bid "to weaken the charisma and strength of Francis". They claim that opponents are attempting to corner the Pope in a battle between liberals and conservatives. The reports also claim that much of the opposition to the Pope comes from conservatives in the United States.

The liberal tone at the synod was criticised by senior bishops including Australia's Cardinal George Pell. In his intervention, he said: "We have no power to change the central teachings of the New Testament or the essential teachings of popes and councils. We are not like Moses, and while we are the successors of the apostles, we are not their equals."

Pell added: "Too many have lost confidence in Jesus's doctrines and doubt or deny that mercy is found in his hard moral teachings. The crucified Jesus was not afraid to confront society, and he was crucified for his pains, teaching his followers that life is a moral struggle that requires sacrifices, and his followers cannot always take the easy options. He did not tell the adulterous woman to continue in her good work, but to repent and sin no more."

This coming Sunday, Pope Francis will canonise Louis and Zélie Martin, the parents of St Thérèse of Lisieux. American author George Weigel, Chair in Catholic Studies, said the canonisation represented "living proof that sanctity in marriage is possible in modernity" and argued that their example applied to all. Weigel warned that the direction the synod was taking would create "an entire, vast class of second-Class Catholics: people whose leaders think them incapable of greatness and immune to the attraction of heroic sanctity; people who thereby come to think of themselves that way."

Cardinal Timothy Dolan, Archbishop of New York, also a conservative, wrote on his blog that those who remained faithful to Catholic teaching were a new "minority" in danger of feeling excluded. "They are looking to the Church, and to us, for support and encouragement, a warm sense of inclusion. We cannot let them down."