The “battle for equality in Northern Ireland” will move to the courts after a vote on legalising same-sex marriage was blocked by the Democratic Unionist Party (DUP), campaigners have said.

A majority of Northern Ireland Assembly members voted in support of legalising same-sex marriage for the first time yesterday.

The Assembly’s fifth vote on the issue was hailed as a “significant milestone” after 53 MLAs voted in favour and 51 MLAs voted against, though the motion was officially defeated due to a petition of concern (POC) filed by the DUP.

In order to pass, a motion subjected to a petition of concern requires support from 60 per cent of MLAs, including at least 40 per cent from both the nationalist and unionist designations.

A previous vote on same-sex marriage fell in April with 47 MLAs in favour and 49 MLAs against.

Patrick Corrigan, Northern Ireland programme director at Amnesty International, said the latest vote showed politicians are “catching up with public opinion”.

He added: “However, the abuse of the Petition of Concern, to hold back rather than uphold the rights of a minority group, means that Stormont has once again failed to keep pace with equality legislation elsewhere in the UK and Ireland.

“The battle for equality in Northern Ireland will now move to the Courts, where same-sex couples have been forced to go to secure their rights as equal citizens in this country.”

Two court challenges to Northern Ireland’s marriage laws are expected to be heard in Belfast in November and December.

The Equality Commission for Northern Ireland has said it remains concerned that LGBT people are “treated less favourably in Northern Ireland than in all other parts of the United Kingdom or Ireland because of their sexual orientation”.