The Supreme Court has ruled that the Government spending of public money on an information campaign on the Children's Referendum was not fair, impartial or equal.
The court held that the information in leaflets and on a website did not conform to the required principles laid down by a landmark judgment, known as the McKenna Judgment.
The principles prohibit the use of public funds to promote a particular outcome in a referendum.
The court ruled that extensive passages in the booklet and on the website did not conform to these principles. The material also included a misstatement.
It granted a declaration that the State acted wrongfully in spending public money on the website, information booklets and advertisements in relation to the referendum.
However, it did not grant an injunction as the court assumed the State will stop distributing and publishing the material.
The case was taken by Mark McCrystal of Kilbarrack Road in Dublin who claimed the Government was wrongly using €1.1m of public funds to promote a Yes vote, something which was not allowed under the McKenna Judgment.
The Government had denied the information campaign was biased towards a Yes vote.
The case was given priority by the Supreme Court as the referendum takes place on Saturday.
The full reasons for the decision will be given next month.
Following the decision the Government website was taken down, however it has since been republished with the wording of the proposed amendment.
Speaking in the Seanad earlier, Minister for Children Frances Fitzgerald said her Department "acted in good faith and with the best intentions to ensure compliance with the McKenna principles" in preparing material for the Government's information campaign.
She said the provision of public information by the Government had at all times been undertaken in good faith based upon the prevailing view as to what was permitted by the McKenna Judgement.
Independent TDs want referendum deferred
A group of Independent TDs have called on the Government to introduce emergency legislation to postpone Saturday's referendum in the light of the Supreme Court judgment.
The TDs said the result of the referendum would be "tainted" as a result of the Government's "bungling".
Accepting that existing legislation did by allow for a postponement, the TDs said the Dáil is sitting tomorrow, and emergency legislation could be introduced.
The five are Mattie McGrath, Shane Ross, Thomas Pringle, Finian McGrath and Tom Fleming.
Minister for Transport Leo Varadkar has said the Yes campaign has not been damaged by the Supreme Court decision.
Mr Varadkar, who is Fine Gael's Referendum campaign director, said this is an issue for the people and it stands on its merits.
He said the courts considered the question of postponement and decided the referendum should go ahead.
Government to review ruling
Minister for Justice Alan Shatter said the Government has to view the detailed reasoning of the Supreme Court, which will be available on 11 December.
Speaking on RTÉ's News at One, Mr Shatter said "it seems there is a very narrow dividing line between government being entitled to give information, to have a right and duty, and being constrained in the manner in which it does this".
However, he said the substance of the referendum proposal is not affected by today's ruling.
Meanwhile, journalist and No campaigner John Waters has said that the Children's Referendum would be a "breach of natural justice" following the ruling.
Speaking on the same programme, Mr Waters said the Government had misappropriated public money in breach of the McKenna Judgment, and if there was a Yes vote, it would be "contaminated".
He added that in seeking to change the Constitution, the Government had behaved unconstitutionally.