Northern Ireland's Health and Social Care Board (HSCB) has been accused of providing misleading information to the Historical Institutional Abuse Inquiry.
The inquiry's chairman, Sir Anthony Hart, criticised the HSCB for its response to a request for welfare records about two children.
He accused the HSCB of "regurgitating" information that the inquiry had already provided to it.
Sir Anthony Hart said: "This is misleading. I am not impressed."
The Historical Institutional Abuse Inquiry (HIA) is examining child abuse in religious and state-run institutions in Northern Ireland from 1922 to 1995.
As part of its investigations, the HIA had asked the HSCB for welfare records about the two children who were sent to Australia in the last century.
More than 100 children from Northern Ireland were shipped to Australia in the mid 1900s, as part of the UK government's child migration policy.
In response to the HIA's request, statements were submitted by the HSCB's acting chief executive, Fionnuala McAndrew.
However, as her statements were being read into the record, Sir Anthony intervened and said the HSCB was providing information that the inquiry had previously given to the board.
Addressing the HSCB's legal representative, Sir Anthony said: "I would be more impressed if your clients, instead of regurgitating what we told you, were able to find these two children's files."
The inquiry's chairman added: "I expect the trust to do better the next time."