The spokesman for Ireland's anti-abortion campaign Save The 8th, has conceded his side has lost the referendum as early polling data suggests 7 out of 10 voters backed reform.
In a statement, communications director John McGuirk said: "The unborn child no longer has a right to life recognised by the Irish state. Shortly, legislation will be introduced that will allow babies to be killed in our country. We will oppose that legislation."
The statement came as counting got under way in Ireland's historic abortion referendum. At the Royal Dublin Society, where counting started at 9am, the mood in the Yes camp was of exhausted jubilance, and as news of Save The 8th's statement, cheers echoed around the hall.
Reacting to the exit polls on Friday night, Taoiseach Leo Varadkar, a vocal proponent of liberalisation, tweeted: "It's looking like we will make history."
On Saturday, as the scale of the victory began to emerge, Varadkar tweeted the landslide vote to repeal in his own constituency of Dublin West.
In Dublin Central, 92% of people voted to repeal the eight amendment, which currently ensures abortions are banned unless a woman's life is in immediate danger.
One poll by national broadcaster RTE suggested around 70% of the electorate have voted to end the country's all but blanket ban on terminations, with another, by The Irish Times, recording 68% in favour of ditching the prohibition.
Colm O'Gorman, executive director of Amnesty International, said he hoped Saturday would be a huge milestone for women's rights. "It looks like the people of Ireland have resoundingly voted to end the 35-year-old constitutional abortion ban.
"In this, Ireland will send a powerful message to women and girls in Ireland and across the globe that their human rights and reproductive health matter.
"That women should be treated with dignity, equality, respect and compassion."
The likely result paves the way for a change in Ireland's legislation on abortion, and speaking on Saturday, the head of the Irish opposition, Michael Martin, said his party would not stand in the way of relaxing the laws.
Pundits had suggested his party's supporters were almost evenly split between Yes and No, and many of his party members in the Dail parliament advocated a No vote. He said the Dail would have to honour the will of the people.
Reacting to the exit poll results, a director at the British Pregnancy Advisory Service (Bpas) said Irish voters have shown that denying women the right to abortion services in their own country in 2018 is not acceptable.
Clare Murphy said: "This is a momentous step forward that is long overdue.
"For decades, Irish women have been forced to travel hundreds of miles to our clinics in England, often alone, at a huge personal and emotional cost.
"The result, once confirmed, means that the Irish government can bring an end to this suffering, and legislate to provide the care women need at home."
On Saturday Ireland's health minister, Simon Harris, said he had called in to the vote count in his home town of Greystones. "Have always known my constituents to be compassionate. Results bear that put - 82% in Greystones box, 83% in Delgany box and around 75% throughout all the county
#togetherforyes," he tweeted.
Ireland's deputy premier, Tanaiste Simon Coveney, another Yes campaigner, said the referendum had made him proud to be Irish.
"Thank you to everybody who voted today – democracy can be so powerful on days like today – looks like a stunning result that will bring about a fundamental change for the better," he tweeted late of Friday night. "Proud to be Irish tonight."
But in the No campaign camp, the mood was one of disappointment. Prominent anti-abortion campaigner Cora Sherlock said: "Exit polls, if accurate, paint a very sad state of affairs tonight," she tweeted late on Friday.
"But those who voted No should take heart. Abortion on demand would deal Ireland a tragic blow but the pro-life movement will rise to any challenge it faces."
The exit polls represent a remarkable turnaround in public opinion in little over a generation. In 1983, 67% citizens voted to insert the Eighth Amendment into the constitution.
The seismic reversal in opinion seems to have been delivered by the younger generations.
People under the age of 53 could not vote in 1983. On Friday, those age groups seem to have backed Yes in overwhelming fashion.
Almost 90% of voters under 25 appear to have voted Yes.