Pope Benedict has described clerical sex abuse as a mystery in an address to Irish Catholics.

The Vatican leader expressed his views via a broadcast at the Mass to close the Eucharistic Congress in Dublin.

Almost 80,000 mass goers at Croke Park on Sunday heard the Papal address.

Irish President Michael D Higgins and Prime Minister Enda Kenny were among the crowd at the final event of the 50th International Eucharistic Congress.

They heard the Pope say: “It is a mystery the fact that people who regularly received the Lord’s body and confessed their sins in the sacrament of Penance could abuse children.”

He added: “Evidently, their Christianity was no longer nourished by joyful encounter with Jesus Christ: it had become merely a matter of habit.”

In the message, relayed after the closing Mass, Pope Benedict noted: “Ireland has been shaped by the Mass at the deepest level for centuries, and by its power and grace generations of monks, martyrs and missionaries have heroically lived the faith at home and spread the good news of God’s love and forgiveness well beyond your shores.

“As Irish Catholics, you are the heirs to a church that has been a mighty force for good in the world, and which has given a profound and enduring love of Christ and his blessed mother to many, many others.

“Thankfulness and joy at such a great history of faith and love have recently been shaken in an appalling way by the revelation of sins committed by priests and consecrated persons against people entrusted to their care.

“How are we to explain the fact that people who regularly received the Lord’s body and confessed their sins in the sacrament of Penance have offended in this way? It remains a mystery.”

The Irish Times reports that Pope Benedict also referred to the 50th anniversary of the opening of the Second Vatican Council next October.

He spoke of how the council had ‘promoted the full and active participation of the faithful in the Eucharistic sacrifice’.

Regarding the introduction of the new missal in English-speaking countries last year, he said that: “Where liturgical renewal since the council was concerned, a great deal has been achieved but it is equally clear that there have been misunderstandings and irregularities.

“Renewal of external forms, desired by the council fathers, was intended to make it easier to enter into the inner depth of the mystery, to lead people to a personal encounter with the Lord, present in the Eucharist.

“Yet, and not infrequently, the revision of liturgical forms has remained at an external level, and active participation has been confused with external activity.

“Much remains to be done on the path of liturgical renewal. In a changed world, increasingly fixated on material things, we must learn to recognise anew the mysterious presence of the risen Lord, which alone can give breadth and depth to our life.”

Closing the Congress, its president and Archbishop of Dublin Diarmuid Martin said: “Over the past eight days the Eucharist has awakened in our hearts something which went way beyond our plans and expectations.

“It has been the nourishment of the extraordinary sense of our communion with one another which those of us who have been in the RDS and are here today have experienced. We have experienced the communion of the church.

“We must go away from here with a renewed passion for the Eucharist. We must go away with a renewed love of the church. We must go away from here wanting to tell others not just about the congress, but about Jesus Christ himself who, in giving himself in sacrifice, revealed to us that God is love.

“In our prayers in these days we have kept in our prayers and in our hearts all those who suffered criminal abuse within the community of Christ’s church and all those who feel in any way alienated from the church and who have not experienced in our church the love of Jesus Christ.”

Papal legate Cardinal Mark Ouellett in his homily said: “I thank wholeheartedly Archbishop Martin, Cardinal Brady and all the collaborators of this event for the gift of their warm hospitality and for the example of their strong dedication to Christian renewal in this country.

“The Irish Eucharistic bell, which resounds from Lough Derg, from Knock and Dublin, must resound in the whole world. Let’s ring the bell further through our personal testimony of renewed faith in the Holy Eucharist.”