A group of Catholic Church abuse victims and their advocates have called on Pope Francis to enforce "zero tolerance" against clerical sex abuse, after completing a six-day pilgrimage to Rome carrying a large wooden cross.

The 10 men and women walked 130 kilometres (81 miles) along the last stretch of the Via Francigena, a medieval trail that connects Canterbury to Rome, ahead of a major Vatican summit on the future of the Church, starting next week.

''And we have come to Rome with a 'Zero tolerance' law that has been drafted by canon lawyers, that will make zero tolerance a universal law of the church," said U.S. attorney Timothy Law, co-founder of Ending Clergy Abuse (ECA).

Sex abuse and cover-up scandals have shredded the Catholic Church's reputation and have been a major challenge for the pope, who has passed a series of measures aimed at holding the Church hierarchy more accountable, with mixed results.

ECA activists came to Rome in the run-up to the synod, an Oct. 4-29 Vatican meeting of world bishops. It is due to discuss, among other things, giving women a greater role in the Church, and the approach towards LGBT people.

"I don't know how you can move into a future if you have not solved the criminal problem of (predator) priests and cover-up by the hierarchy in the Catholic Church," Peter Isely, another U.S.-based member of ECA, said about the synod.