Referendum campaign: The Taoiseach, Mr Ahern, has claimed that Ireland will continue to have "the most liberal citizenship law in Europe" if the referendum is passed on June 11th.
The Tánaiste, Ms Harney, and the Minister for Justice, Mr McDowell, also defended the proposal yesterday.
Mr Ahern rejected suggestions that the referendum proposals will undermine the human rights of children and said the proposal will not affect the Belfast Agreement.
He said in a statement that a Yes vote would "not remove citizenship from anyone who had it or was entitled to it prior to the enactment of the amendment".
A Yes vote would not prevent those who do not acquire citizenship at birth from acquiring it at a later stage after a number of years residency in the country, Mr Ahern said.
He described as "unfounded" claims that the Government proposal would affect the rights of children.
"Every person in Ireland, regardless of whether they are citizens or not is fully entitled under national and international law to have their human rights fully respected," Mr Ahern said.
"It is a separate matter for the people of every country to decide whom and under what circumstances they grant citizenship." The referendum was designed to close a loophole in the current citizenship regime which was open to abuse, Mr Ahern said.
He said its purpose was to replace an unqualified right to citizenship at birth regardless of how briefly either of the parents of a child has been in Ireland "with a qualified but liberal provision" for citizenship.
"Under the legislation that the Government will enact if the referendum was passed, a child either of whose parents has been in Ireland for three of the previous years will be entitled to citizenship," he said.
"In recent days unfounded claims have been made alleging that children born in Ireland might be rendered stateless as a result. This is totally untrue. Any child born in Ireland who would for some reason not be entitled to citizenship in any other state would now and would continue to be automatically entitled to Irish citizenship."
Ms Harney said voters should recall that the non-national spouses of Irish people were required to wait for three years after marriage and be resident in Ireland for three years before they can become Irish citizens.
"Similar requirements are found in the laws of many countries, for example, Canada, Denmark, Germany, France, the UK and the US," she said.
"Any non-national person who is resident in Ireland for five years is eligible to become an Irish citizen. This would apply to many people who are contributing to our society on work permits. It is accepted as a reasonable way to show that citizenship is valued and not too easily acquired." Mr McDowell accused Labour's foreign affairs spokesman, Mr Michael D Higgins, of "repeated ignorance, arm-chancing and repeated factual inaccuracy" during an interview on the RTÉ Morning Ireland programme on Monday.
Mr Higgins said he accepted Mr McDowell's contention that he had made an error in relation to the Nigerian constitution but insisted that he had been "completely correct" in his assertions about the German citizenship regimes.
Mr Higgins said the tone of Mr McDowell's attack on him was "vulgar" and said his own case remained fundamentally the same.
While all children born in Ireland before the amendment would have Constitutional protection on their citizenship, he said those born to non-Irish non-EU parents would have only legislative protection if the referendum was carried.