Angela Kerins claims the spending watchdog had no power to call her before a hearing to explain her management of the charity's finances.
The Minister for Health Simon Harris, Minister for Transport Shane Ross and Deputy Sinn Féin leader Mary Lou McDonald are just three of the seventeen named defendants in Angela Kerins' legal action.
They, along with fellow members of the 2014 Public Accounts Committee, including its then Chairman John McGuinness, are accused of acting outside their powers by calling her before a seven hour hearing.
During that time, she was quizzed about her management of the Rehab Group, which was coming under huge pressure to explain its salary and pension bill.
She was on 240,000 euro before she stepped down as CEO.
In her court papers, Ms. Kerins says she spent over a week in hospital because of the hearing and has called the watchdog's jurisdiction into question.
A special three-judge panel, presided by President of the High Court Mr. Justice Peter Kelly, was convened to hear her action, which is due to begin later this morning.
