An amendment to the equal marriage bill for England and Wales, calls for a referendum on the issue of equal marriage, and would mean that even if passed at all stages, the law would not come into effect until voters approved it at a referendum.

The amendment, tabled by Labour peer Lord Anderson of Swansea, Conservative peer Lord Cormack, and crossbench peer Lord Singh of Wimbledon, calls for a referendum on equal marriage to be held on 7 May 2015, or if that date is unsuitable, it would be required to take place before 1 June 2016.

The question which would be raised for the referendum is: “At present, the law in England and Wales defines marriage as the union of a man and a woman. Should the law be changed to define marriage as the union of two people—whether a man and a woman, or woman and a woman, or a man and a man?”.

The amendment states that, even if the bill is passed at all stages, it would not be able to come into effect until a majority of voters at the referendum vote in its favour.

It reads: “The Secretary of State may not bring any part of this Act into force unless the referendum provided for at section (Referendum provisions) delivers an affirmative outcome.”

All three of the peers who tabled this amendment voted in favour of a Lord Dear amendment, which was not approved, yet which would have stopped the Marriage (Same Sex Couples) Bill from being given a second reading.

The Marriage (Same Sex Couples) Bill comes back in committee the week commencing 17 June. It will have its report stage on 8 July and third reading on 15 July.

Ministers are hoping that the bill will have Royal Assent before summer recess, at the end of July.

Another amendment tabled by Lord Mackay of Clashfern, would allow straight couples to enter into civil partnerships, amidst fears that such an amendment could wreck the bill.

Former Archbishop of Canterbury, Lord Carey, has also tabled a bill which could wreck the equal marriage bill for England and Wales, by suggesting that there be two “tiers” of marriage.

Equal marriage critic Lord Dear has proposed another, similar amendment to the Marriage (Same Sex Couples Bill), protecting those who believe marriage is “the union of one man and one woman for life to the exclusion of all others.”

Out4Marriage has launched the LobbyALord website in order to make it easy for members of the public to lobby Peers on the issue.