THERESA May will oppose plans to let MPs vote to liberalise Northern Ireland’s highly restrictive abortion laws, Downing Street signalled yesterday.

The indication came after it emerged the Prime Minister is facing open revolt from senior Conservative women backing reform in the six counties following a landslide vote in the Irish Republic to lift a ban on terminations.

Responding to the historic vote, Penny Mordaunt, the UK Government’s women and equalities minister, tweeted over the weekend that the hope for change in Northern Ireland “must be met” amid calls for a referendum to be held there.

But Downing Street fears legislating in Westminster to relax abortion laws in Northern Ireland will destabilise the May government by antagonising the 10 Democratic Unionist Party MPs who prop up her administration. The DUP is opposed to any move to lift abortion restrictions.

Northern Ireland is the only place in the British Isles where abortion is in most circumstances illegal. The UK’s 1967 Abortion Act was never extended there, and terminating a pregnancy is only allowed if there is a serious risk to the woman’s mental or physical health.

A Downing Street source said yesterday that May believed abortion reform was “an issue for Northern Ireland” and that the issue highlighted the need for the power-sharing executive at Stormont, which has been in abeyance since it collapsed in January last year, to be restored.

But many MPs want the House of Commons to settle the issue, and the Labour MP Stella Creasy has said she intends to force a vote by tabling an amendment to the forthcoming domestic violence bill.

Sir Vince Cable, the LibDem leader, yesterday said the talks deadlock in Northern Ireland meant the Westminster government was entitled to take the initiative.

“In Northern Ireland women have suffered from antiquated, inhumane criminalisation for far too long. Theresa May cannot remain silent on this issue,” he said. “Since there is, effectively, direct rule from Westminster, the UK Government has the responsibility. It can and should take the opportunity to deal with this issue properly.”

Anne Milton, the UK skills minister, told the BBC she thought there would be “a significant majority” in the Commons in favour of liberalising the abortion laws. Abortion is traditionally a matter on which MPs are given a free vote.

Under the Sewel convention, the UK Government has agreed it will not normally legislate on matters that are the responsibility of devolved administrations without their consent. On those grounds ministers could try to prevent a vote taking place on the domestic violence bill, or on other legislation.

Mordaunt tweeted on Saturday: “Based on the exit poll, a historic and great day for Ireland, and a hopeful one for Northern Ireland. That hope must be met.” She did not say she thought it was for the Commons to change the law, but a report in a Sunday newspaper she said she favoured MPs having a free vote, as do the four previous women and equalities ministers: Amber Rudd, Justine Greening, Nicky Morgan and Maria Miller.

Polls to date have revealed strong support in Northern Ireland for relaxing abortion laws in some circumstances, although not to the extent allowed in the rest of the UK.

Sinn Fein, the second-largest party in Northern Ireland, supports limited change to the country’s abortion laws. Michelle O’Neill, its leader in Northern Ireland, on Sunday said the country was “becoming a backwater” because of the position taken by the DUP.