Parallel Westminster bills calling for same sex marriage in Northern Ireland represent the biggest step in the ongoing campaign to lift the ban, activists have said.
Identical private members' bills will be tabled in the Lords and Commons this week, one by a Conservative peer and the other by a Labour MP.
Lord Hayward and Conor McGinn are spearheading efforts to legislate for the contentious issue at Westminster amid ongoing political deadlock over the matter at Stormont.
The ban on same sex marriage is one of the disputes at the heart of the powersharing impasse in Belfast, with the DUP resisting Sinn Fein calls for a law change.
Engaged Belfast couple Cara McCann and Amanda McGurk (pictured) are travelling to Westminster on Tuesday to campaign for action. They intend to hand a 30,000-signature petition in at Downing Street on Wednesday.
After meeting Belfast Lord Mayor Nuala McAllister on Monday, Ms McCann, who is a wedding singer, said:"We are over there to put a human a face on things, just to let people know the real story and why people think we should have marriage equality here in the north.
"It starts tomorrow. It's going to be long journey ahead of us but it's a start in the right direction. We are getting married on St Valentine's day next year, so we are hoping it will not be a civil partnership and we are hoping it will a marriage by that time.
"This is the biggest step we have had to date since the campaign started. We weren't having any luck here and I think the majority of people here don't really care how they get marriage equality. If it's from here or if it's to be brought in from Westminster - I think the most important thing is that we get it."
Her fiancee Ms McGurk added: "I think it is ridiculous that we don't have the same rights as everybody else, we get charged the same taxes and we don't get any concessions because we don't have the same rights, so why can't we have the same rights as everybody else?
"We are not going to take anybody else's rights away by having ours, so I don't see what the problem is."
Lord Hayward said it was an honour to table the bill in the Lords.
"It gives me great honour to launch the Westminster campaign for equal marriage rights in Northern Ireland in the House of Lords," he said.
"I am pleased to introduce the Marriage (Same Sex Couples) (Northern Ireland) Bill in the Lords with the support of the Love Equality campaign from Northern Ireland.
"The strength of public opinion for equal marriage rights in Northern Ireland
will be shown by the petition they are due to present to Downing Street later this week."
Patrick Corrigan of the Love Equality campaign said: "Lord Hayward's bill, in parallel with Conor McGinn's bill in the Commons later this week, is a powerful demonstration of cross-party, cross-parliamentary support for equal marriage in Northern Ireland.
"We call on the UK Government to introduce its own legislation to ensure equality can now become law for Northern Ireland couples. Discrimination against LGBT couples in Northern Ireland can no longer be tolerated."
Copyright (c) Press Association Ltd. 2018, All Rights Reserved. Pictured (c) Niall Carson / PA Wire.