Former chief executive and board member of Rehab Group Frank Flannery and former chief executive Angela Kerins have written to the Dáil Committee on Procedures and Privileges about the PAC.
Mr Flannery has asked the CPP to address how to repair alleged damage done by the Public Accounts Committee going outside its remit in relation to matters associated with him during recent hearings.
Ms Kerins has also written to the CPP, claiming that the PAC's inquiry is unlawful.
Her letter says there was a patent lack of jurisdiction as the Rehab Group's accounts are not audited by the Comptroller and Auditor General.
She said this also meant that the CPP could not grant the PAC's application for compellability.
Ms Kerins appeared before the PAC for seven hours in late February.
The PAC has sought to compel Mr Flannery, a former Fine Gael strategist, and Ms Kerins to appear, but was told last week by the CPP to provide more details of why it wishes to be given compellability powers.
In a move viewed by some PAC members as a refusal to grant these powers, the CPP said Rehab was not audited by the Comptroller and Auditor General and it also asked for the PAC to name the individuals it wanted to compel.
The PAC is seeking independent legal advice on how to proceed with what is the first application to the CPP about compellability.
In a letter to the PAC in April, Mr Flannery said he was extremely concerned about his rights as a private citizen under the Constitution and his reputation.
He claimed the committee had acted outside its remit and was abusing its powers.
The decision by the CPP may have implications for it dealing with the report from the Interim Administrator of the Central Remedial Clinic John Cregan, as the CRC is also not audited by the C&AG.
The report, which is with the Health Service Executive, is due to go to the PAC tomorrow.