Members of the prime minister’s own cabinet immediately joined opposition leaders and backbenchers in demanding new laws in Northern Ireland to legalise abortion.
Pro-abortion MPs claim that since devolved government in the province is currently suspended the UK government in Westminster should now grasp the opportunity to change the law.
But any move to liberalise the abortion law will be bitterly opposed by the Tories’ allies at Westminster, the DUP, whose MPs are insisting Northern Ireland must not be bullied into a change.
Although there was no word from the PM in the hours immediately after the result of the Irish referendum, the government’s Women and Equalities Minister Penny Mordaunt welcomed the vote.
Backed by her four predecessors in the role in calling for a free vote of MPs on a change in the law, Ms Mordant tweeted: “A historic & great day for Ireland, & a hopeful one for Northern Ireland.
“That hope must be met. #HomeToVote stories are a powerful and moving testimony as to why this had to happen and that understanding & empathy exists between generations. #trustwomen.”
The Labour leader Jeremy Corbyn tweeted: “Great news that the Republic of Ireland has voted to #Repealthe8th to support a woman’s right to choose.
“Congratulations to everyone who has taken part in this inspiring campaign and to everyone who travelled home to vote. A fantastic victory for women’s rights.”
The Liberal Democrat leader Sir Vince Cable said in an interview: “The position in Northern Ireland is now highly anomalous and I think, probably, action will now have to be taken.”
Asked if Mrs May should intervene, he said: “As long as you have devolved elected bodies then one has to respect their preferences, whether it’s Scotland, Wales, Northern Ireland or London.
“Since there is, effectively, direct rule from Westminster, the government has responsibility and it can and should take the opportunity to deal with this issue properly.”
Scotland’s first minister, Nicola Sturgeon, tweeted: “Congratulations to @Together4yes and the people of Ireland. Compassion, justice and trust in women win the day.”
But the campaigning Labour backbencher Stella Creasy said that while the landslide vote in Ireland was a historic moment the battle was not over yet.
“Repealing the Eighth Amendment is clearly a huge step forward but campaigners will now look to liberalise the law in Northern Ireland,” she wrote in the Sun on Sunday.
“There are now 2.5 million women who have won the right to choose in the country. Put simply, we have to focus on the 1 million women north of the border.
“Abortion is illegal there in all but the most exceptional of circumstances and those unable to travel because of coercive relationships risk life imprisonment.
“One mum is awaiting trial in Belfast after buying abortion pills for her daughter – this isn’t right. The United Nations has even condemned the British government over violating the rights of women there.
“It’s good to see cabinet ministers such as Penny Mordaunt hailing the referendum a historic and great day. But now we need deeds not words – they must back our call for legislation fit for the 21st century.”
But the Democratic Unionist MP Ian Paisley served notice that his party would block any change in the law, declaring that Northern Ireland “should not be bullied into accepting abortion on demand”.
He added: “The settled will of the people has been to afford protections to the unborn life and protect the life of the mother.”
And attacking the “foaming at the mouth idiocy” of some commentators, Mr Paisley added: “On Abortion NI has had a settled cross-party view on this for decades. Nothing suggests it has changed.”
The pressure for abortion reform now presents the prime minister with another potential nightmare as she battles to win Commons votes with no majority and depending on the DUP for a majority.
She already faces the prospect of knife-edge votes on the EU Withdrawal Bill in the Commons next month as she attempts to overturn 15 defeats inflicted by the House of Lords with some pro-Remain MPs poised to rebel.
So all the signs are that Mrs May will back the DUP in its opposition to changing the abortion law in Northern Ireland, even if it means alienating the opposition parties and some of her own MPs.
But if a number of Conservative MPs – emboldened by the stance of Ms Mordaunt and other women ex-ministers – threaten to rebel on abortion, she will face a massive dilemma.
Although the government has been winning votes against Labour and the other opposition parties in the past couple of weeks, the PM still relies on the DUP’s 10 MPs to win those votes.
A breakdown in the Tories’ so-called “confidence and supply” arrangement with the DUP would be unthinkable for the prime minister.
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At worst, it could bring her government crashing down and trigger a general election if she started to lose important commons votes, on Brexit, for instance.
Which perhaps explains the prime minister’s silence in the hours after the Irish referendum result.