A member of the Public Accounts Committee has called for its terms of reference to be extended if members are refused permission to question former Rehab bosses Angela Kerins and Frank Flannery.
The Committee on Procedure and Privileges is due to issue new rules on compelling witnesses.
It is expected they will preclude PAC calling the former executives on the basis that Rehab is not a State agency.
Fine Gael TD Simon Harris has said if that happened, the PAC should seek to have its terms extended.
He Taoiseach Enda Kenny and the leader of the Opposition, as well as the committee, had said Ms Kerins and Mr Flannery should appear.