Pope Francis says the heart-wrenching pain of sex abuse victims was "long ignored, kept quiet or silenced."
He's responded to new reports of clerical sexual abuse and the ecclesial cover-up.
A report last week detailed sex abuse by hundreds of priests in the US state of Pennsylvania.
In a letter published on The Vatican website, the Pope calls on the church to be close to victims in solidarity, and to join in acts of prayer for those "atrocities".
"Crimes that inflict deep wounds of pain and powerlessness, primarily among the victims, but also in their family members and in the larger community of believers and nonbelievers alike.
"We feel shame when we realize that our style of life has denied, and continues to deny, the words we recite." #PopeFrancis responds to reports of clerical sexual abuse in a #letter addressed to the whole People of #God. Read the full text here: https://t.co/Ol9NDcedD7
— Vatican News (@VaticanNews) August 20, 2018
"We abandoned them"
"Looking back to the past, no effort to beg pardon and to seek to repair the harm done will ever be sufficient.
"Looking ahead to the future, no effort must be spared to create a culture able to prevent such situations from happening, but also to prevent the possibility of their being covered up and perpetuated.
"The pain of the victims and their families is also our pain, and so it is urgent that we once more reaffirm our commitment to ensure the protection of minors and of vulnerable adults."
Pope Francis adds: "With shame and repentance, we acknowledge as an ecclesial community that we were not where we should have been, that we did not act in a timely manner, realising the magnitude and the gravity of the damage done to so many lives.
"We showed no care for the little ones; we abandoned them."
"Frustrated and disappointed"
The One in Four charity, which works with those who have been affected by child sex abuse, said it was 'frustrated and disappointed' with the Pope's response.
One in Four Director Maeve Lewis. Photo: Sam Boal/RollingNews.ie
Executive Director Maeve Lewis said: “There is nothing in this new communication from Pope Francis to show that the Vatican intends to put in place clear laws and protocols that will hold every bishop and cardinal who shield sex offenders and place them in positions where they can continue to abuse children.
"Survivors are tired of meaningless apologies and expressions of solidarity that do not involve a clear call to action.”
She added: “The Pope’s visit is very distressing to many survivors, retriggering old emotions of shame, humiliation, despair and anger.
"The least they deserve during this papal visit is a clear commitment that the Catholic Church finally intends to deal with clerical child sexual abuse.”