The NI Public Services Ombudsman (NIPSO) has threatened a complainant with the Official Secrets Act.
It related to tweets made by a health service patient who had made a complaint to NIPSO.
The BBC's Nolan Show has raised questions about the legality of the threat issued.
NIPSO said the ombudsman "welcomes the discussion around the publication of her reports".
The patient, Carol McCullough, has been involved in an ongoing dispute with NIPSO.
She made a complaint to the ombudsman about medical treatment she received.
Mrs McCullough, a transplant patient with complex health issues, then received a legal letter threatening her because she had disclosed the ombudsman's report into her complaint.
The letter warned her that the Official Secrets Act might apply.
She said if NIPSO "don't have confidence to share their reports, how can the public have confidence in them".
Mrs McCullough had tweeted extracts of the NIPSO report relating to a health diagnosis made by an independent expert employed by NIPSO.
Mrs McCullough says the expert did not meet her to assess her condition.
The Nolan Show has sought legal advice which disputes the assertions made by NIPSO that it has the power to stop Mrs McCullough sharing her report.
The Ombudsman, Marie Anderson, did not comment on specific questions put to her by the Nolan Show about the Official Secrets Act threat.
In a statement NIPSO told the programme that "the ombudsman believes that she has acted appropriately" and within the law.
Last year the Nolan Show reported on a contempt threat issued to a complainant, Gregory Burke, for sharing the findings of another NIPSO report with government officials.
The programme has obtained a copy of a letter from the attorney general for Northern Ireland to NIPSO, prompted by Mr Burke's case, in which John Larkin's office stated that Marie Anderson did not have the power to threaten citizens with contempt.
"That the ombudsman herself considers the report to be confidential until she decides to publish it is irrelevant…. because the ombudsman has no power to make an order restricting publication she ought not to threaten citizens with contempt proceedings when there is no apparent basis for subjecting their proposed actions to such a sanction," said the letter.
In the statement to the Nolan Show NIPSO said: "She [Marie Anderson] will continue to publish her reports when it is in the public interest to do so through a process guided by the principles of openness and transparency. However, complainants, independent professional advisors, public bodies and others involved in an investigation entrust her with their most sensitive information and opinions.
"The ombudsman must act to protect this information where she sees a potential breach of confidentiality."
The NIPSO letter quoted legislation which prevents the ombudsman's predecessor - the commissioner for complaints - from disclosing information. However, the Nolan Show has sought legal advice which disputes the assertions made by NIPSO that this prevents Mrs McCullough disclosing extracts from the report.
Official Secrets Act
The 2016 letter from NIPSO stated that it "consider(s) the publication of these extracts from the draft report to be so serious as to also constitute contempt" and warned that they may constitute an offence under the Official Secrets Act.
An attachment to the letter described penalties for convictions under the act. These include "imprisonment for a term not exceeding two months or a fine or both".
The Nolan Show understands that the threat relates to a series of tweets made by Mrs McCullough to NIPSO in the run-up to the Ombudsman's letter of 28 July 2016.