Though same-sex couples in the UK have had civil partnerships since 2004, marriage is currently restricted to opposite-sex partners.
Opponents of the bill have said civil partnerships are the same or similar to marriages and extending marriage to same-sex couples is unnecessary. They argue partnerships have a ‘separate but equal’ status, giving same-sex couples the same rights as straight couples.
However there are key differences between the two kinds of union.
Read the full story.