The Chairman of the Public Accounts Committee said it received correspondence from Eames Solicitors about former Rehab chief executive Angela Kerins on 9 May.
The PAC sought compellability powers earlier this month for the attendance of Ms Kerins and former chief executive Frank Flannery.
John McGuinness said the PAC has informed Ms Kerins that the application for compellability is a parliamentary procedure from one Dáil committee to another.
Mr McGuinness said Ms Kerins was told there is no procedure whereby those who may be the subject of the compellability can have an input into that process.
He said the application for compellability has been submitted and the PAC is awaiting a response from the Committee of Procedures and Privileges.
He said: "The CPP will more than likely seek outside legal advice on the application relevant to the examination of the Section 39s.
"We will have to wait on the result of their meeting and their advice before we continue, so there is no timeframe, unfortunately."
He was responding to a question from Independent TD Shane Ross.
Mr McGuinness said he expects that the legal advice should not take that long and the PAC should know before the summer recess.
The committee agreed to write to the CPP to ask that it makes the issue a priority.