A threat to close a newspaper because it reprinted topless pictures of the Duchess of Cambridge has been described as an "over the top reaction" by the National Union of Journalists (NUJ).
The Irish Daily Star published the photographs on Saturday, after they had appeared in French magazine Closer.
The tabloid's co-owner, Richard Desmond, said he was "taking immediate steps to close down the joint venture".
The NUJ said it was "disproportionate" to threaten to cut more than 100 jobs.
NUJ Irish secretary, Seamus Dooley, said the closure threat was "a callous and crude attempt by Northern and Shell to protect their UK commercial interests", and he claimed that the company had shown "no regard for the livelihood" of its Irish workers.
"The Irish Daily Star has always been marketed as an Irish title free of UK interference in editorial matters. The editor took a controversial decision on this issue just as he and his predecessors have done in the past, without reference to the newspaper owners."
Mr Dooley added: "There are agreed mechanisms for dealing with breaches of editorial standards and it is difficult to see why these mechanisms were not used rather than the sledge hammer deployed by the UK partners of the newspapers."
Both co-owners of the Irish Daily Star have criticised the decision of its editor, Mike O'Kane, to publish the pictures.
However, like the NUJ, INM has also described Mr Desmond's threat to close the title as disproportionate.
INM said Mr O'Kane's "regrettable" editorial decision was now under investigation but also pointed out that more than 120 staff are currently employed at the Irish Daily Star, directly and indirectly.
Mr Dooley said the contrast between the reactions of the two co-owners was interesting.
"If you're a 50% shareholder in a tabloid newspaper which concentrates on very serious politics, sport and an element of celebrity, you can't then throw a hissy fit and, because of one incident, pull the plug and put 70 workers plus maybe another 30 freelances out of work - it is a disproportionate reaction.
"He (Mr Desmond) is entitled to say to his editorial team 'I'm not happy with the decision'. I thinks it's interesting to contrast with Independent News and Media - the other shareholder - who said 'this shouldn't happen, it was a bad call, we're going to review it, but we think its disproportionate'."
Mr Dooley said it would be "quite difficult" for INM to sustain the newspaper without the support of its UK partner.
The general secretary of the NUJ, Michelle Stanistreet, is to write to Mr Desmond on Monday, to express the union's concerns over his remarks.
She has described the closure threat as "an over-the-top reaction which should be reconsidered calmly and with consideration of the full implications for Irish journalism and for editorial diversity".
Lawyers acting for the Duke and Duchess of Cambridge are due in court in Paris later to try to restrict publication of the pictures.
It is expected they will ask French prosecutors to bring criminal charges against the photographer.