Pope Francis today apologised for the clerical abuse that has rocked the Catholic Church during his first meeting with victims since his election to papacy.

The Pontiff gave a Mass this morning in which he addressed adult victims of sexual abuse, telling them: "For some time now I have felt in my heart deep pain and suffering.

"So much time hidden, camouflaged with a complicity that cannot be explained until someone realised that Jesus was looking."

Denouncing the crimes as similar to those of a "sacrilegious cult", Francis asked "for the grace to weep, the grace for the Church to weep and make reparation for her sons and daughters who betrayed their mission, who abused innocent persons.

"Before God and his people I express my sorrow for the sins and grave crimes of clerical sexual abuse committed against you. And I humbly ask forgiveness," he implored, according to Reuters.

Francis later met privately with six victims, two each from Britain, Ireland and Germany, apparently spending around half an hour with each individual.

He has been particularly vocal in his condemnation of sexual abuse in recent months, following years of allegations levelled at the Catholic Church regarding the behaviour of priests and other clergy.

In May he denounced sex abuse as "an ugly crime...because a priest who does this betrays the body of the Lord".

He also compared abuse to devil worship; describing it as like "a satanic Mass" and adding that "we must go ahead with zero tolerance".

Despite this, however, the Pope has been subject to much criticism for his failure to act quickly on the matter, and David Greenwood, Chairman of Stop Church Child Abuse, told Christian Today that today's offering is insufficient.

"I cannot understand why any survivor of clergy sex abuse would want to meet the Pope. My view is that the Pope should be visiting them in their own homes and begging their forgiveness," Greenwood said in May.

"Successive Popes have made and promoted rules for Bishops and priests which have shielded clergy from investigation by the police throughout the world. The church's lamentable behaviour has been criticised by survivors, lawyers and now two United Nations committees (the committee for the rights of the child and the committee against torture) yet Pope Francis and other senior clerics continue to defend the church."

Anne Doyle of Bishops Accountability, a US-based group dealing with abuse in the Catholic Church, was more positive about today's meeting.

She told Reuters: "I think it's very important that the pope meet with victims."

"We know that this pope is capable of compassion and his refusal to meet with sexual abuse victims so far has been inconsistent with the mercy he has shown with so many marginalised. This is something that he had to rectify."

Since his election Francis has set up a committee which focuses solely on clergy abuse – a move that has been welcomed by many campaigners.

"The Church is aware of this damage, it is personal, moral damage carried out by men of the Church, and we will not take one step backward with regards to how we will deal with this problem, and the sanctions that must be imposed," he promised in April.

"On the contrary, we have to be even stronger."

Furthermore, Vatican spokesman Federico Lombardi insisted that today's meeting was more than just a publicity stunt.

"If you see the persons that come out of this meeting with the Pope, you will understand it's not a public relations event. It is a very profound, spiritual encounter, dialogue with a father, a person who tries to understand deeply," he said.