The High Court has ruled the first meeting of the Seanad can only lawfully be held with 60 members in place.
10 Senators took a case, seeking a declaration the upper house can meet and pass legislation, without the Taoiseach's 11 nominees.
In a 62 page judgment, the three High Court judges hearing this case rejected arguments from the 10 senators that the Seanad can legislate with 49 members and not the Taoiseach’s nominees.
The Senators were disputing the State's view the upper house can only sit when the taoiseach nominates their appointees.
The case had some urgency as legislation around the Offences Against the State Act and the Special Criminal Court would lapse at midnight tonight if a government wasn't formed.
The court said it was satisfied Article 18.1 “clearly and unambiguously means the Seanad “must be comprised of sixty members, eleven of whom are nominated and forty nine of whom are elected”.
*Reporting by Shane Beatty