Ireland's premier, Leo Varadkar, must clarify comments he reportedly made at an event in New York, the National Union of Journalists has said.
It has been claimed that the Taoiseach criticised the media at the private event, saying it is one of the few issues on which he can sympathise with US President Donald Trump.
According to reports, when Mr Varadkar was asked about Mr Trump's attacks on the media, he said the media was not interested in the truth but in the story.
NUJ Irish general secretary Seamus Dooley called for the Taoiseach to clarify his comments.
He said: "Respect for freedom of expression is a core value of the UN.
"Attributed comments are damaging to Ireland's reputation as a modern democracy, given Trump's views on press freedom."
The Taoiseach was in the US to launch Ireland's bid for a seat at the United National Security Council.
In a statement, a spokesman for the Taoiseach said: "The lunch, hosted by Ireland's Consul General in New York, was a private event.
"Attendees included young Irish people based in New York working across a range of sectors, including media, finance and tech. They shared a wide-ranging discussion.
"This conversation is now being quoted selectively and out of context.
"The Taoiseach believes that a free, fair and balanced press is a cornerstone of our democracy."
The Times and Irish Times reported that, during the private event, Mr Varadkar was particularly critical of the political press and claimed that the journalists were more interested in gossip at Ireland's Parliament, Dail Eireann, than in the workings of the government.
Labour Party leader Brendan Howlin said: "The Taoiseach may believe that 'a free, fair and balanced press is the cornerstone of our democracy', but his deeds and moral leadership carry more weight.
"No-one doubts that Ireland's links to the United States of America are hugely important, and that such trips to New York are strategically valuable to Ireland's interests.
"But whatever about criticising the media when at home on the campaign trail, for Ireland's head of government to attack the Irish media when on a diplomatic and strategic trade mission is wholly inappropriate."
Sinn Fein president Mary Lou McDonald said Mr Varadkar must clarify the "disparaging" remarks.
She said: "The remarks as reported are very troubling and the Taoiseach should clarify and explain what he said.
"The freedom of the press to write, broadcast and report freely in the public interest and to do so without coercion, without pressure and without undue influence is vitally important.
"Of course, this flows both ways and the media is not above criticism and must be able to stand over its reporting."