Angela Kerins is taking legal action to try and stop the investigation by the Public Accounts Committee (PAC) into her former role as chief executive of Rehab.
Her lawyers claim the questions put to her by the Committee last February about her salary, her car and bonus entitlements suggest PAC was engaged in a witch hunt against her.
She claims the Committee acted beyond its remit and demonstrated bias.
Her solicitor Aidan Eames (centre) explained why she is taking legal action
The High Court heard she suffered a collapse of health following her voluntary attendance five months ago.
The application is being made on an ex-parte basis.
She has released a statement through her solicitor Aidan Eames explaining why she is now taking legal action against the Committee.