Theresa May is under pressure to give MPs a free vote on legalising abortion in Northern Ireland after the Republic of Ireland voted comprehensively in favour of reform.

The prime minister is facing calls from within her Cabinet to scrap the ban on abortion and bring it in line with the rest of the UK.

It creates a fresh headache for Ms May, whose parliamentary majority relies on the support of the Democratic Unionist Party (DUP), which is fiercely anti-abortion.

However, the prime minister is believed to consider the matter an issue for the Northern Irish assembly, which has been without a government since January 2017 after power-sharing collapsed.

A referendum in the Republic of Ireland on Friday saw 66.4 per cent of voters back overturning the country’s abortion ban.

Abortion is currently only legal in Northern Ireland if the life or mental health of the mother is at risk.

Among those now pushing for reform of the law are understood to be Penny Morduant, the international development secretary, who also holds the women and equalities brief.

Ms Morduant called the Irish vote a "historic and great day for Ireland" and a "hopeful one for Northern Ireland".

"That hope must be met," she added.

Reports suggest she has the support of several other former cabinet ministers, including Amber Rudd, Nicky Morgan, Justine Greening and Maria Miller. All have previously held the women and equalities role.

Ireland votes in historic abortion referendum: in pictures Show all 15 1 /15 Ireland votes in historic abortion referendum: in pictures Ireland votes in historic abortion referendum: in pictures Members of the public hold yes placards on Fairview road Getty Images Ireland votes in historic abortion referendum: in pictures Taoiseach Leo Varadkar casts his vote at Scoil Thomas, Castlenock Dublin PA Ireland votes in historic abortion referendum: in pictures Members of the public hold no placards on Fairview road Getty Images Ireland votes in historic abortion referendum: in pictures A woman wears a campaign T-shirt and badges REUTERS Ireland votes in historic abortion referendum: in pictures A woman arrives to vote with a baby as Ireland holds a referendum on liberalizing its law on abortion, in Dublin, Ireland, May 25, 2018. REUTERS/Max Rossi MAX ROSSI REUTERS Ireland votes in historic abortion referendum: in pictures Lorraine Curtin with her son Cillian Curtin, age 5 months, and Petrina Conmee arrive at Dublin airport from Portugal, having traveled especially to vote in Ireland's referendum REUTERS Ireland votes in historic abortion referendum: in pictures Members of the public hold yes placards on Fairview road Getty Images Ireland votes in historic abortion referendum: in pictures A nun casts her ballot REUTERS Ireland votes in historic abortion referendum: in pictures Handout photo of Micheal Martin and wife Mary voting in Cork as as the country goes to the polls to vote in the referendum on the 8th Amendment of the Irish Constitution. PRESS ASSOCIATION Photo. Picture date: Friday May 25, 2018. See PA story IRISH Abortion. Photo credit should read: PA Wire NOTE TO EDITORS: This handout photo may only be used in for editorial reporting purposes for the contemporaneous illustration of events, things or the people in the image or facts mentioned in the caption. Reuse of the picture may require further permission from the copyright holder. PA PA Ireland votes in historic abortion referendum: in pictures Ireland's Prime Minister Leo Varadakar leaves a polling station after casting his vote AFP/Getty Images Ireland votes in historic abortion referendum: in pictures Tom Harrington arrives to cast his ballot at Knock national school AP Ireland votes in historic abortion referendum: in pictures President Michael D Higgins and his wife Sabina cast their votes at the polling station in St Mary's Hospial, Pheonix Park, Dublin, as the country goes to the polls to vote in the referendum on the 8th Amendment of the Irish Constitution. PRESS ASSOCIATION Photo. Picture date: Friday May 25, 2018. See PA story IRISH Abortion. Photo credit should read: Niall Carson/PA Wire Niall Carson PA Ireland votes in historic abortion referendum: in pictures Leo Varadkar casts his vote PA Ireland votes in historic abortion referendum: in pictures A woman carries her baby as she arrives to vote Reuters Ireland votes in historic abortion referendum: in pictures Nuns prepare to cast their ballots as Ireland holds a referendum on liberalizing its law on abortion, in Dublin, Ireland, May 25, 2018. REUTERS/Alex Fraser STAFF REUTERS

Ms Morgan called the result of the Irish referendum "a huge milestone in the history of the Republic of Ireland and, I believe, the right decision".

Ms Rudd added: “Well done the voters of Ireland.”

However, the DUP are certain to strongly resist any plans to give MPs a free vote on the issue.

One of the party’s MPs, Ian Paisley, said: “Northern Ireland should not be bullied into accepting abortion on demand.

“Northern Ireland did not have a constitutional imperative on abortion, it is governed by laws that can be changed.

"The settled will of the people has been to afford protections to the unborn life and protect the life of the mother," he said.

Irish abortion referendum: Celebrations at Dublin count centre as results come in

Ms May could face pressure to allow her MPs a free vote on an amendment tabled to the upcoming Domestic Violence Bill by Labour MP Stella Creasy.

Ms Creasy claims more than 140 parliamentarians have already pledged their support.

Liberal Democrat leader Sir Vince Cable also backed reform and said the prime minister should act in the absence of the devolved government in Belfast, which has been suspended since early last year as the parties struggle to reach an agreement.

He said: "The position in Northern Ireland is now highly anomalous and I think, probably, action will now have to be taken."