The legal proceedings were brought by a graduate of the University of Limerick who claimed that the Oireachtas had failed to meet a constitutional obligation to extend the franchise for electing university members beyond the University of Dublin and the National University of Ireland.

The appellant, Tomás Heneghan, initially took the case as a lay litigant and was later represented by legal rights group FLAC.

In a judgment handed down on Friday, Mr Justice Gerard Hogan agreed that there was a constitutional obligation on the Oireachtas to extend the franchise as a result of the Seventh Amendment of the Constitution (Election of Members of Seanad Éireann by Institutions of Higher Education) Act 1979.

The declaration of unconstitutionality has been suspended until 31 July 2023 when the parties will have the opportunity to make submissions on how the judgment should be implemented. As a result, the decision will have no legal effect on any election or by-election in the meantime.

Eilis Barry, chief executive of FLAC, congratulated Mr Heneghan on his “courage, fortitude and persistence in taking this landmark case for democracy, equality and the rule of law”.

Sinéad Lucey, managing solicitor at FLAC, added: “This judgment is significant in terms of the importance of the expression of the will of the people in a constitutional referendum and confirming that the Oireachtas cannot ignore the outcome of a referendum.

“The significance of the case goes beyond the issue of votes in the Seanad as a profound reflection on a democratic nature of the State.”

Mr Heneghan said: “I’m thankful to the court for their sincere consideration of the arguments put forward. My legal team have also been extraordinary in their work and support over the past three years, particularly FLAC, Sinéad Lucey, Rosario Boyle SC, James Kane and Emma Sinnott.

“I hope the Oireachtas now acts speedily to ensure that the democratic right to vote in Seanad elections is extended to all, regardless of educational or socio-economic background.”