The Love Equality campaign has called upon Theresa May’s government to actively enforce marriage equality in Northern Ireland to bring it in line with the rest of the United Kingdom.

Campaigners have urged legislative action after the collapse of the Stormont Talks, which focussed on political discussion around restoring devolution to Northern Ireland.

Same-sex marriage became legal in England and Wales in March 2014, and shortly followed in Scotland in December 2014.

Northern Ireland Secretary of State Karen Bradley has said that if the issue came before Parliament, they would allow a free vote on it.

“In accordance with the Belfast Agreement, this is a devolved matter which should be addressed in the NI Assembly; but the power of the Westminster Parliament to legislate remains unaffected,” she stated in a written answer.

“If this issue were to be raised in Westminster, the Government’s policy is to allow a free vote on matters of conscience such as equal marriage.”

Patrick Corrigan of the Love Equality campaign for civil marriage equality said: “The outcome of the political talks has been deeply disappointing.

“Even if the parties had reached a deal on the basis of the widely reported draft, marriage equality legislation at Stormont would have been doomed to failure, given the lack of agreement on reforming the Petition of Concern.

“We have no confidence in the prospects of the proposed review of the Petition of Concern, given the failure of the parties to agree any reform as part of the talks themselves.”

Related: Why we must act now to bring marriage equality to Northern Ireland

He added: “Sadly, equal marriage appears not to have been a sufficient political priority in these talks. On the basis of the leaked deal, Northern Ireland’s LGBT community was looking at the prospect of four more years of second-class citizenship.

“That is not good enough and we demand change.

“We are calling on the UK Government to introduce legislation at the earliest opportunity to bring Northern Ireland’s laws on marriage equality into line with the rest of the UK.

“We welcome the positive tone of the Secretary of State’s answer today, that the government would allow a free vote on the issue, but it falls short of what is now required.

“In every other jurisdiction in the UK and Ireland, it has been government legislation which has ensured equality for same-sex couples. The rights of LGBT people in Northern Ireland to be treated equally should not be left to the lottery of the Private Member’s Bill process.

“The Government can fix this problem and be assured of overwhelming support across both Houses of Parliament. It should do so without further delay.”

Last week, a group of LGBTQ teenagers delivered a petition of more than 14,000 signatures to the Secretary of State’s office calling for the UK government to deliver marriage equality legislation at Westminster.

In November 2015, a majority of MLAs in the Assembly voted to support equal marriage, but the measure was blocked by the DUP using a Petition of Concern, a voting mechanism designed to protect the rights of minorities in Northern Ireland.

What’s more, according to a poll in 2016, 70% of the Northern Irish public were in support of marriage equality.