The Garda Fraud Bureau is investigating a complaint by former Fine Gael strategist Frank Flannery that a confidential letter received by a Dail committee may have been unlawfully leaked.
The letter, written by developer John Kelly to the Public Accounts Committee (PAC), made a series of allegations related to Rehab Group, the charity and commercial organisation where Mr Flannery was once chief executive.
The correspondence was considered by the committee in private last March and it decided to forward the letter to Garda headquarters, owing to the seriousness of the claims.
The Garda Bureau of Fraud Investigation subsequently began examining the allegations made by Mr Kelly, which related to plans he had to buy Rehab's headquarters.
However, the Irish Independent has learned that officers are also investigating a complaint made by Mr Flannery after a number of media organisations gained sight of the letter.
Mr Flannery, who is no longer involved with Rehab, sat on its board in recent years and also acted as a lobbyist for the group.
Under Section 35 of the Ethics in Public Office Act 1995, it is an offence for a person to disclose information obtained by him or her by being present at a sitting of an Oireachtas committee held in private.
Detectives have been making inquiries in recent weeks to ascertain whether the letter was leaked by someone associated with the committee or was given to the media by another source.
Officers from the fraud bureau have asked a number of people for statements and plan to prepare a file for the Director of Public Prosecutions.
Although the committee puts much of the correspondence it receives on its website, the Kelly letter was not published.
Commenting under committee privilege at the time, PAC chairman John McGuinness said Mr Kelly's statement "contains several serious allegations against named individuals who have or had associations with the Rehab Group".
The allegations "could potentially involve criminal wrongdoing" and the committee decided to forward the correspondence to gardai, pursuant to its obligations under the Criminal Justice Act 2011, he said.
Rehab subsequently issued a number of statements saying various allegations had been put to it by members of the media, all of which the group considered to be "utterly false and defamatory".
In the letter, Wicklow businessman Kelly claimed he had discussions with former Rehab chief executive Angela Kerins and her then PR advisor Michael Parker about buying the group's headquarters in Sandymount, Dublin.
He also claimed to have spent over €100,000 on flights and hospitality for Ms Kerins and others in a bid to increase his chances of securing the deal.
Ms Kerins, who left Rehab in April, rejected the claims she had discussed selling the property, while Mr Parker also denied the claims and said he was handing the matter over to his lawyers. Rehab also said it had at no point considered selling its headquarters to Mr Kelly. It said Ms Kerins had social dealings with Mr Kelly which were totally unrelated to the business of the group.