LONDON — Roman Catholic bishops in the Netherlands said Friday that they offered “sincere apologies” to victims of sexual mistreatment, hours after a report by an official commission said church officials had “failed to adequately deal with” abuse affecting as many as 20,000 Dutch children in Catholic institutions.

It remained unclear, however, whether the report broke significant new ground in a tortured debate over the relationship between sexual abuse and Catholic institutions.

Based on a survey of more than 34,000 Dutch adults 40 and over, the report said that 10 percent of them had suffered from some form of abuse while they were children — a proportion that doubled to about 20 percent among those who had spent some of their youth in institutions, irrespective of their affiliation.

Referring to the probability of minors’ being sexually abused in institutions rather than in any other location, the report said, “It emerged that the risk was twice as high as the national average, but with no sufficient difference between Roman Catholic and non-Roman Catholic institutions.”