A senior member of the Sisters of Nazareth order of Catholic nuns has apologised to children who were abused while in the care of the congregation in a home in Derry.
Sister Brenda McCall was giving evidence at the Historical Institutional Abuse Inquiry in Banbridge.
She said that the sisters are deeply sorry if any child was abused or emotionally neglected while in their care.
Sister McCall said that having listened to evidence at the inquiry, which was very shocking and harrowing, they must accept that, at certain times, by certain sisters, things were just not right.
Meanwhile, a former Catholic bishop has said nuns at the centre of the inquiry were taken for granted.
Edward Daly, 81, expressed admiration for a religious order caring for thousands of troubled children amid the violence and "abominable" poverty of 1960s Northern Ireland.
Bishop Daly said in 36 years of ministry he only heard one complaint, from a woman separated from her brothers as a child and sent from a home to Australia, but had no involvement in running the centres.
He said: "They were doing work that needed to be done, that nobody else was doing."
The treatment of young people, orphaned or taken away from their unmarried mothers, in houses run by nuns, brothers or the state is a key concern of an investigation chaired by retired High Court judge Sir Anthony Hart.
It is considering cases between 1922, the foundation of Northern Ireland, and 1995.