The No side in the family and care referendums accused Ministers of using interest groups to fight a proxy Yes case for constitutional change.

Senator Michael McDowell and Aontú leader Peadar Tóibín said the lack of independent scrutiny raised questions about the McKenna ruling of the Supreme Court, which bans the spending of public money.

The gap emerged when the Standards in Public Office Commission and the new Electoral Commission said they had no power to examine whether non-government organisations (NGOs) comply with the Supreme Court ruling.

The ethics watchdog said: “While the Standards in Public Office Commission has a role under the Electoral Act 1997 in regard to third parties receiving donations for political purposes, including for a referendum campaign, it has no role concerning the expenditure of public monies by non-governmental organisations in the circumstances to which you refer.”