Pope Francis has acknowledged “with shame and repentance” the Catholic Church’s failure to act on allegations of sexual abuse by clerics against minors going back decades, writing “we showed no care for the little ones; we abandoned them.”

In an unusually blunt letter released by the Vatican on Monday, the Pope wrote, “I acknowledge once more the suffering endured by many minors due to sexual abuse, the abuse of power and the abuse of conscience perpetrated by a significant number of clerics and consecrated persons.

“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.”