In a two-hour hearing in Geneva, the Committee Against Torture launched a barrage of questions to the Vatican delegation, asking about past policy decisions, the juridical distinction between the Holy See and Vatican City, and information on specific cases.
The Vatican, which will issue its formal answers today, said the Church has been "doing its own house cleaning" for 10 years, was determined to protect children and that measures put in place have led to a decline in cases of sexual abuse of children by priests.
George Tugushi, a committee member from Georgia, said an international commission advising Pope Francis on how to deal with sexual abuse was a very positive step but not enough.
"The commission may need help to ensure all cases are reported properly and begin to change the climate of impunity but it cannot be considered in our opinion as a substitute for a functioning investigation system," he told the Vatican delegation headed by Archbishop Silvano Tomasi.
Another committee member, Satyabhoosun Gupt Domah of Mauritius, asked if the Holy See was taking steps to eliminate the "chemistry that creates the conditions" for sexual abuse of children by priests.