The Government does not have the right to change the State's official name at EU meetings to "Éire Ireland" and the move could be legally challenged, Fine Gael MEP Gay Mitchell has said.
Minister for Foreign Affairs Dermot Ahern, he said, made "a unilateral decision" by changing the State's official name for EU business without receiving the sanction of the Oireachtas.
Last year, the EU decided that Irish would become the EU's 21st official and working language requiring translation at all relevant meetings from next year.
Mr Mitchell said: "Article 4 of the Constitution of Ireland states that 'The name of the State is Éire or, in the English language, Ireland'. The Constitution does not say the name of the State is Éire and Ireland, nor is it Éire Ireland.
"Using Éire Ireland to designate the State is of doubtful legal validity. It is not provided for in the Constitution or the Republic of Ireland Act 1948, which states in section 2 'The description of the State shall be the Republic of Ireland, in Irish Poblacht na hÉireann'. That Act itself repealed the Executive Authority (External Relations) Act, 1936, which described the State (in Irish only) as Saorstát Éireann," he said.
Urging the Government to put the matter for debate before the Oireachtas European Affairs Committee, Mr Mitchell said: "Could we please have some discussion on this before we make more changes? Surely the name by which the State is referred to abroad should be determined by democratic process and not ministerial whim."