In the wake of the emphatic vote to legalise abortion across the Republic of Ireland, senior MPs at Westminster have called for Northern Ireland to rescind its conservative abortion laws too. In Northern Ireland, where abortion is illegal in all but the most exceptional circumstances, the Democratic Unionist Party has stood firm against any possible changes.

Meanwhile, Arlene Foster, the leader of the DUP, has said with regards to Brexit that maintaining alignment between Northern Ireland and the UK is a red line. One which, if crossed, would result in May losing the support of the 10 DUP MPs that prop up her government.

Senior figures at Westminster have called out this alleged hypocrisy. If Arlene Foster is so committed to full alignment between Northern Ireland and the rest of the UK, then this should extend to social issues too, namely abortion and gay marriage, her critics say.

Labour MP Jess Phillips tweeted: “I’m with Arlene, NI shouldn’t be treated different to rest of UK. So tomorrow I expect the Government to announce that women in NI will have the same rights as my constituents. Thanks Arlene.”

The problem with this statement is that, in fact, there is no ideological inconsistency in Arlene Foster’s position. Devolution exists for the sake of maintaining the Union, while still allowing for regional specificities. So, Ms Foster can simultaneously call for alignment over how Brexit treats Northern Ireland and the UK, while still allowing for abortion to be a devolved issue.

If abortion laws are to change in Northern Ireland, it should be a matter for Stormont and not Westminster – this is obviously how devolution works. One problem (among the litany of others) is that there is no functioning government at Stormont now, and it looks as if May might be taking matters into Westminster’s hands.

The Sun reported yesterday that she held a secret meeting with a few senior Tory women MPs who are vocal about changing the law on abortion in Northern Ireland.

Amber Rudd, Justine Greening, Penny Morduant (the Minister for Women and Equalities) and Karen Bradley (Northern Ireland Secretary) were summoned to Number 10. The latter two are the ministers who would be responsible for any change in the law.

This move will undoubtedly rile May’s Northern Irish allies, but more interestingly it throws into sharp relief the question over whether matters like abortion should be devolved issues at all. Foster asserted her principles on abortion on Sky News this week. She said she understood the DUP to be “the only party that supports the unborn,” in Northern Ireland and pledged to fight on the national stage. But if devolution exists to allow for regional specificities, then they should not be used as leverage in a row with Westminster.

There are risks for Foster, with the fast-changing views on social affairs of younger voters coming to the fore. With Ireland having voted for legalisation of abortion just last month, and gay marriage just three years ago, if Belfast doesn’t guarantee the rights of the people of Northern Ireland, the risk for Unionists is that new voters may start looking to Dublin to do so. That could undermine the Unionism that Foster so emphatically endorses.

Whatever the outcome, the row now poses an existential threat to May’s government. Foster could withdraw the DUP support that props up the government run by May if she believes the Tory leader is committed to seeking a withdrawal of the stringent abortion laws in Northern Ireland.