The Democratic Unionist Party (DUP) has once again blocked progress on same-sex marriage legislation in Northern Ireland, having effectively vetoed a motion to legalise it through a ‘petition of concern’.

The proposed motion was being pushed by Sinn Fein following an overwhelming vote in favour of a referendum on legalising same-sex marriage in the Republic of Ireland.

The Stormont Assembly will debate the motion on Monday 29 April, but it will now fail due to the petition of concern lodged by the DUP.

A petition of concern requires a motion to have a majority of support from unionist and nationalist Members of the Legislative Assembly (MLAs) in order to progress.

As the DUP has the most MLAs of any party their petition is effectively a veto against same-sex marriage.

Peter Weir, chief whip of the DUP, said: “It is only a few months since the Assembly last debated this issue and views were clearly expressed at that time.

“It has been made very clear that same-sex marriage will not be introduced in Northern Ireland and the DUP is tabling a Petition of Concern to ensure that this motion will not be carried.”

He added that the DUP was “the only party to have a united position in opposition to the redefinition of marriage”.

Sinn Fein’s Caitriona Ruane countered: “What the DUP need to do is go out and explain to the gay and lesbian people in their communities why they are blocking equality. Equality threatens nobody.”

A previous motion in Northern Ireland was put forward in October 2012, but was defeated by the Democratic Unionist Party (DUP).