Tánaiste Eamon Gilmore, who is agnostic, sought and received legal advice on swearing a religious oath when he attends the Council of State meeting on proposed abortion legislation on Monday.

The Constitution requires Council of State members at their first meeting to say: “In the presence of Almighty God I do solemnly and sincerely promise and declare that I will faithfully and conscientiously fulfil my duties.”

The Atheist Ireland organisation has written to Mr Gilmore describing the oath as one "that a conscientious agnostic cannot honestly make", but Mr Gilmore's spokesman said he respected the Constitution and would comply with his constitutional obligations.

Mr Gilmore’s spokesman said the wording of the oath was set out in the Constitution and could not be changed without a referendum.

“The Tánaiste believes that the oaths and affirmations required as a matter of law should be as inclusive as possible. That said, it is not proposed to hold a referendum on the matter,” he said.

Chairman of Atheist Ireland Michael Nugent called on Mr Gilmore to make "constitutional history" by refusing to make the declaration required under Article 31.4.

Mr Nugent argued Mr Gilmore would be the first Irish person to be asked to swear a constitutional oath “in the presence of a god that you are publicly on record as not believing in”.

He said the Tánaiste would create a precedent by whether he chose to take the oath or not. “Either you will be seen as a politician of principle who will literally go down in the history books of Irish constitutional law on the issue of freedom of belief and conscience in Irish politics,” he said.

“Or else you will perpetuate the idea that swearing an oath means nothing in Ireland as you can do it with a metaphorical wink, and nobody really cares.”

The Council of State is comprised of the Taoiseach, Tánaiste, Chief Justice, President of the High Court, Ceann Comhairle, the two former presidents, the five former taoisigh, retired chief justices, as well as those named by Mr Higgins. They are: Michael Farrell, Deirdre Heenan, Catherine McGuinness, Gearóid Ó Tuathaigh, Ruairí McKiernan, Sally Mulready and Gerard Quinn.

The meeting will take place at Áras an Uachtaráin next Monday afternoon.