The three Opposition party leaders have said they would legislate for the X case in Government.
The Fine Gael leader, Mr Michael Noonan, Labour leader Mr Ruairí Quinn and Green Party leader Mr Trevor Sargent held a joint press conference yesterday to call for a No vote in the referendum.
In a joint statement they said they believed the Taoiseach, Mr Ahern, had deliberately misinterpreted the choice before the Irish people on Wednesday.
"The choice is about the X case - to repeal it or confirm it, not about abortion on demand. If this referendum is defeated the law on abortion in Ireland will not change and while the Taoiseach may be prepared to turn his back on cases like X and C, we are not."
Mr Noonan said: "In government, with our partners, we would legislate to reflect in statute law the decision as reflected in the Supreme Court judgment in the X case." Mr Quinn said legislating for the X case was the position of his party but it was not the task now to try and draft and "spell out" the nature of the legislation.
Mr Sargent said the Government was digging itself into an even deeper hole with the referendum. He said it should reflect on what had happened since it introduced its proposals, particularly given the case of Ms Deirdre de Barra. Ms de Barra is carrying a foetus with a congenital abnormality that means it cannot survive outside the womb - her letter outlining her case was published in The Irish Times this week.
Mr Quinn said this case had been "one of those threshold moments" in the campaign. He said these particular circumstances needed to be examined to see if the law needed to be changed.
On this issue Mr Noonan said it was his understanding that different medical consultants took different views and there should be freedom between a woman and her consultant. "It seems perverse to impose an obligation on a woman who is pregnant to carry the child to term who, according to medical fact, will be stillborn or die after delivery."
Meanwhile, the former Taoiseach, Mr John Bruton, wrote to the Fine Gael chairman, Mr Padraic McCormack, this week expressing concern at the party's intention to legislate for the X case. The letter was discussed at a parliamentary party meeting on Wednesday. According to one TD, Mr Bruton, who has said he will be voting Yes, said in the letter he felt there had not been enough discussion about the proposed legislation.
At the press conference Mr Noonan said Mr Bruton was "absolutely right" when he said there was not agreement on the detail of that legislation within the parliamentary party. "As a parliamentary party we decided on January 15th that the party position would be to look for a No vote and to campaign actively. It was recognised that a small minority of people did not agree with the majority view."
The three party leaders said that if carried, the amendment would confirm the criminalisation of women who had abortions and expose them to sentences of up to 12 years in jail.