Gay rights campaigners are urging Theresa May to intervene and introduce equal marriage in Northern Ireland after they lost their legal challenge yesterday.
Mr Justice O'Hara dismissed two cases challenging Northern Ireland's ban on same sex marriage and said it was up to Stormont, not the courts, to decide social policy.
Rainbow Project director John O'Doherty said that, as the Assembly wasn't functioning, it was now a matter for Westminster. He appealed directly to the Prime Minister to act.
Mrs May's government is reliant on DUP support at Westminster, and the Northern Ireland party has repeatedly thwarted efforts to legalise same-sex marriage at Stormont.
"It is the responsibility of Theresa May's government to make the necessary amendments to the marriage legislation to make it applicable in Northern Ireland," said Mr O'Doherty.
"The eyes of LGBT people around the world will now be on Theresa May.
"She says that she has changed her mind on LGBT equality over her years in Parliament.
"Now is her chance to prove it."
Mr O'Doherty added that the two couples who took the case would consider an appeal.
Grainne Teggart of the Love Equality campaign said it was unacceptable that Northern Ireland was the only part of the UK where gay marriage was illegal.
"The majority of people in Northern Ireland want to live in a country where unequal laws are consigned to the history books.
"It's time politicians reflected the will of the people and urgently legislate for equality," she said.
Sinn Fein MLA Caral Ni Chuilin said gay people had to resort to the courts because equal marriage had been denied by the DUP "in defiance of wider public opinion and a majority in the Assembly".
She added: "The ongoing denial of rights by the DUP, with the support of the British government, which are enjoyed by citizens right across these islands is unacceptable. This is an issue which is at the heart of the current political crisis.
"The fight for marriage equality will go on."
Ms Ni Chuilin also tweeted it was ironic that her brother's marriage was "recognised in London where he lives but not in Belfast where he was born".
Alliance MLA Paula Bradshaw described the High Court's ruling as "bitterly disappointing" and said there was anger and despair in the LGBT community.
"Progress would have been an extremely positive step forward, allowing people of every background to get the respect they deserve, and I would urge all those feeling let down today not to give up hope - equal marriage is still within our reach."
SDLP leader Colum Eastwood MLA said Northern Ireland was "the only small corner of these islands where we maintain a hierarchy of love".
He said: "We are increasingly isolated here and across Europe as a place where the commitment and compassion of a same-sex couple is not recognised in our law.
"This ruling reinforces the fact that a failure of politics is to blame for the inequity and inequality that loving couples here face.
"Reform of the petition of concern can unlock this and so many other issues.
"Let those who claim to be democrats put down the weapons of veto and vitriol."
Green Party MLA Clare Bailey said that she was "disappointed but not defeated" after the High Court ruling.
"I respect the decision of the court, but remain determined to play my part as a public representative to deliver marriage equality," she said.
"The Green Party brought the first motion on marriage equality before the Assembly back in 2011. We know that the majority of MLAs are in favour of change.
"We need to restore the devolved institutions and get equal marriage back on the Assembly agenda.
"This is about real people, their lives and their love."
Northern Ireland Humanists coordinator Boyd Sleator said: "Northern Ireland's ongoing discrimination against same-sex couples brings shame on us all.
"We hope the judgments are appealed, and that one day soon, our lawmakers will accept that love is love, and will at last bring the law in line with public opinion, which overwhelmingly favours marriage equality."