The chairman of the Dáil's Public Accounts Committee has said the committee has the power to compel Rehab director Frank Flannery to appear and answer questions.
However John McGuinness has urged Mr Flannery to appear before the committee on a voluntary basis to discuss his role in setting the pay of senior managers.
Figures on both sides of the political divide have called on Mr Flannery - a former senior strategist for Fine Gael - to attend and answer questions.
Our political correspondent Gavan Reilly reports;