A UK MP has said he is "very confident" that MPs across all parties will endorse same-sex marriage for people in Northern Ireland if his amendment is selected this week.

Similar legislation was blocked by the DUP in 2015 despite support for the move from a majority of members of the Northern Ireland assembly.

Speaking on RTÉ's Morning Ireland, Armagh-born British Labour party MP Conor McGinn, who has tabled an amendment to the bill that would allow same-sex marriage in the North, said that has been trying to get Northern Ireland to be in line on the issue both with the UK and the rest of the island of Ireland.

Mr McGinn said: "I've been trying to get Northern Ireland to be in line with both the rest of the UK and the rest of the island of Ireland in terms of legalising same-sex marriage or equal marriage.

"What I'm proposing this week is that if the Stormont executive isn't up and functioning again by the 21st of October, which is the deadline in the bill itself proposed by the Secretary of State, that we would at Westminster legislate to make same-sex marriage legal in Northern Ireland."

Asked about the likelihood of the bill getting the support of majority of MPs at Westminster, Mr McGinn said that if his amendment is selected and is seen as "in scope in terms of the bill", then he is "very confident" that the MPs across all parties in the House of Commons will emphatically endorse equal rights for people in Northern Ireland.

"If it is called and selected and seen as in scope in terms of the bill, then I am very confident that that the MPs across all parties in the House of Commons in - what would be a free vote - will emphatically endorse equal rights for people in Northern Ireland that they can enjoy with the rest of Ireland and the rest of the UK."

With the passing of the legislation through the House of Commons being conditional on the failure to get Stormont back up and running by the October deadline, Mr McGinn added that he would much prefer the decision on same-sex marriage to be taken at Stormont.

With no executive at Stormont since January 2017, he reiterated that the LGBT community in Northern Ireland should not have to wait for equal rights.

He said that they were giving the politicians at Stormont and both governments "three months to sort this out; and if they can't sort it out, we'll sort it out".

Asked about the possible support for another amendment to the Northern Ireland bill tabled by Dominic Grieve, Mr McGinn said this is the "biggest issue facing the UK and his constituents", most acutely felt in Northern Ireland.

The amendment put forward by the former Conservative party attorney general is designed to prevent the UK leaving the EU with no deal, blocking the capacity of whoever becomes the next prime minister to have a no deal exit. 

He said he will be supporting Dominic Grieve's proposal and he knows many across the House of Commons will. 

"This is the biggest issue facing the UK, facing my constituents. And arguably facing Ireland as well. But it's most acutely felt in the North. 

"I grew up in a border community in south Armagh. The concerns, the fears, the real worries of the people there that the UK will leave with no deal are - as they say - very acute.

"So what Dominic Grieve is proposing is that through this legislation we effectively rule out leaving with no deal. 

"I will be supporting him and I know many of my colleagues across the House of Commons will."