A No vote in Wednesday’s abortion referendum would ultimately lead to abortion on demand, according to the Taoiseach, Mr Ahern.
Mr Ahern was speaking at the final Fianna Fáil press conference urging a Yes vote before the moratorium on the abortion referendum comes into effect.
When asked if he thought that a No vote would lead down the slippery slope of abortion on demand, Mr Ahern replied: "Yes, I do".
The Taoiseach also said that if the Government’s proposal was defeated it would very difficult for any Government to revisit the issue and it would not be something he would "be returning to in a hurry".
"This issue has been discussed at enormous length over the last few years ... where do you draw the line in the sand? ... where do you make definitions? I don’t know if any Government could back it to it and make those decisions," said the Taoiseach.
On the issue of the legal status of the morning after pill, Mr Ahern said that the "statement of the Irish Medicines Board that it believes that emergency contraception is legal and can be licensed has provided independent reinforcement of our unequivocal advice on this matter".
The Minster for Health and Children, Mr Micheál Martin said: "Good law and decent solutions to human problems come out of complex information, out of paving attention to detail, out of seeking consensus. Good law and decent solutions come out of acknowledging when consensus is not possible and offering - in good conscience - the option which achieves the general good".