Fine Gael has risked a split among the 15 Independents, whose support Enda Kenny is trying to gain, by moving to address the abortion issue.
The acting Taoiseach included proposals for a citizens' assembly on the Eighth Amendment in a document supplied to the Independents - most of whom were unaware that the idea was even on the table during their 50 hours of talks.
Seven of the group engaged in coalition talks are opposed outright to any constitutional change regarding abortion, while a number of others have serious reservations.
Mattie McGrath has already informed the Fine Gael negotiating team that he will immediately walk away if they insist on the assembly.
Seán Canney, Michael Fitzmaurice, Noel Grealish, Michael Collins and the Healy-Rae brothers are also opposed to any changes to the law.
However, Katherine Zappone told the Irish Independent last night: "I will not sign up to any Programme for Government that does not address a referendum on the Eighth Amendment."
In a 122-page document supplied to Independents, Fine Gael said it wanted to establish a citizens' assembly, without the participation of politicians, that would make recommendations to the Dáil on potential changes to the Eighth Amendment.
The law gives equal status to the right to life of a mother and her unborn child.
A similar discussion paper given to the Independents by Fianna Fáil makes no reference to abortion legislation.
Galway West TD Seán Canney said the issue had never been mentioned during his talks with Fine Gael. "If Fine Gael has an agenda to bring that in, they can do it on merit in the Dáil. It shouldn't be in the Programme for Government," he said.
Similarly, Roscommon's Michael Fitzmaurice said: "I would definitely be saying that if it's a thing in the Programme for Government, I'm against it.
"I wouldn't be in favour of it, end of story. I think we'd want to get rattling on housing, health and other things before that."
Mr McGrath said there was "no way" he would support Mr Kenny's election as Taoiseach unless Fine Gael dropped the plan, which originated in its election manifesto.
Michael Healy-Rae said: "I was surprised that it wasn't kept out of there" (the discussion document). The Kerry Independent said he was "very, very concerned" about the development but added that he would not stop a citizens' assembly if he had a deciding vote.
"I just have some worries - but then you have to try be balanced. If people want to have a say on the matter, it's hard to deny them that. It would cause me a great concern but, having said that, let them have a view or an opinion."
Earlier this year, his brother Danny voted in favour of a motion that came before Kerry County Council, calling on the Government not to take any action to repeal the Eighth.
Maureen O'Sullivan and Denis Naughten told the Irish Independent they were cautious about any legal changes but would support the idea of a citizens' assembly.
Kevin 'Boxer' Moran said he was entirely opposed to abortion but would not have a problem with the assembly.
His fellow Independent Alliance members Shane Ross and John Halligan are open to changes in the abortion laws, while Finian McGrath said: "I'd be very supportive of it. I signed up to the Repeal the 8th campaign before the election. As a compromise, I'd support a constitutional convention."