Sinn Féin TD Pa Daly has been given permission by the High Court to take his legal challenge to the attendance of so called super-junior ministers at Cabinet meetings.
Mr Daly said the Constitution limits the number of Government ministers to 15 and binds them to confidentiality about their discussions.
The attendance of extra Ministers of State is not contemplated by the Constitution, he has argued.
His Senior Counsel, Feichin McDonagh said they wanted to get the case heard "as soon as possible".
He said it was possibly a case which might be heard by a three judge, divisional court, which is formed to hear cases of constitutional importance.
The court was told the application for leave to seek judicial review relates to the appointment of ministers of state with rights to attend Cabinet.
Mr Daly wants declarations that their attendance at Cabinet by virtue of the Government's designation is unconstitutional.
He has claimed the Taoiseach and Government have failed to act in accordance with the democratic process.
He said they can hold a referendum to amend the Constitution if they want to increase the size of Government.
The super juniors who have been appointed are Hildegarde Naughton of Fine Gael as well as Seán Canney and Noel Grealish of the Regional Independent Group.
Fianna Fáil’s Mary Butler has been appointed Government Chief Whip as well as a super junior minister with responsibility for Mental Health.
Ms Justice Mary Rose Gearty gave permission to Mr Daly to take the case. She said it had reached the necessary bar of being an arguable case with a prospect of success.
It will be back before the court next Tuesday.
Mr Daly who is represented by Mr McDonagh as well as barristers, Brendan Hennessy and John Biggins and solicitor, John Rogers is taking his action against the Taoiseach, the Government, Ireland and the Attorney General.
The first time the practice of appointing "super junior" ministers occurred was during the 1994 "Rainbow Coalition" of Fine Gael, Labour and Democratic Left, when Pat Rabbitte was permitted to attend cabinet meetings.
Mr Daly said it appears the practice has continued since then, but he said it is inconsistent with the Constitution.
