THE Government was warned by a senior judge that its own private referendum information campaign caused confusion among voters, it can be revealed.
The High Court judge's advice will place further pressure on government ministers after they still went ahead with their information project for the Children referendum.
The campaign cost more than €1m and was subsequently ruled unlawful by the Supreme Court.
The new revelation comes after the referendum was passed by 58pc to 42pc – a far smaller margin than was predicted.
The shocking turnout of only one in three voters was the third-lowest on a referendum polling day.
The Coalition also has the threat of a court challenge to the result hanging over it after the Supreme Court ruling.
Ministers are expected to look at what can be done in future referendums in light of the McKenna judgment, which prevents taxpayers’ money being spent to support a government proposal.
The Government was warned by High Court judge Kevin Feeney that its controversial information booklets – delivered along with the independent referendum watchdog's literature – had caused confusion among voters during the previous referendum, on the EU Fiscal Treaty.
In its report on that vote held last May, the Referendum Commission, headed by Mr Justice Feeney, said its research after the event found the dual campaigns caused problems.
The critical comments on the Government's information campaign are contained in the conclusions of the report provided to the Department of the Environment in August. But the report has yet to be released.
Aside from the Referendum Commission's research, it is thought the Coalition would have conducted its own research, which could have made the same finding.
Despite the judge's warning, the Government proceeded with its own information campaign, separate to the Referendum Commission, in the Children's referendum.
The final two days of the campaign were overshadowed by the Supreme Court rap across the knuckles for the Government.
Five judges in the highest court in the land found the Government's information booklet and website was "not fair, equal or impartial".
The court ruled the Coalition had "acted wrongfully" in spending €1.1m as it breached the McKenna judgment of 1995.
That ruling says taxpayers' money cannot be spent in advocating a particular side in a referendum.
As a result of the Supreme Court's ruling, the Government is expecting a challenge to be brought against the Children referendum result, though it is highly unlikely to succeed.
Campaigners from the No camp want to see the result tested in the courts.
Former MEP and disability rights activist Kathy Sinnott said the result was "contaminated" and should be challenged.
Political analysts said the Supreme Court ruling damaged the turnout and the Yes vote.
The Children's referendum saw the lowest turnout for 16 years, with three constituencies voting No -- Donegal North-East, Donegal South-West and Dublin North-West.
Fine Gael sources pointed out that these three constituencies all have a strong Sinn Fein presence and sitting TDs. Recriminations also began in public, with shots being fired between the Coalition and the opposition.
Based on the pattern of the results, junior minister Shane McEntee accused Sinn Fein and Fianna Fail of talking out of both sides of their mouths during the campaign.
The Government will face questions in the Dail this week from Fianna Fail leader Micheal Martin about the handling of the campaign, particularly the information element.
Children's Minister Frances Fitzgerald's role in drafting the wording and Attorney General Maire Whelan in signing off on it will come under particular scrutiny.
Ministers will also consider what to do about information campaigns in future, given the constraints of the McKenna judgment.
Government sources believe that overturning the McKenna judgment is "not a runner" as it would probably require a referendum itself.
In future, the Government will probably have to leave the information to the Referendum Commission or fund both sides, which is unlikely.
"Being unable to use any government money to explain the proposal that you as a Government are making, that's going to be harder to win referendums in future," a minister said.
"Parties can't afford to pay for multiple referendum campaigns every year. But we'll really have to see the judgment before coming to conclusions."
The Supreme Court will issue its full written judgment in a month's time.
Social Protection Minister Joan Burton rejected suggestions that the low turnout on Saturday would weaken her hand when it came to arguing against child benefit cutbacks at the cabinet table.
"Not at all. We'll be having discussions about the Budget in the next few weeks," she said.
Child benefit payments are at risk of being cut again in the Budget because savings of €540m are required from the Ms Burton's department.