Culture Secretary Maria Miller will propose that the Public Order Act be amended to protect critics of same-sex marriage in today’s House of Lords committee on the same-sex marriage bill.

The Public Order Act 1986 includes several clauses prohibiting the provocation of hatred or violence. Mrs Miller’s amendment would clarify that criticism of same-sex marriage is not such an offence.

Numerous equal marriage opponents have voiced fears that the passing of the bill would lead to their prosecution. The amendment would be an attempt to placate those fears by making it clear people cannot be prosecuted for voicing their opinion on same-sex marriage.

It would add a clause to the Public Order Act which states that “any discussion or criticism of marriage which concerns the sex of the parties to marriage shall not be taken of itself to be threatening or intended to stir up hatred.”

The Government amendment is one of several expected to be confirmed by the Lords whip, Baroness Stowell, at the committee stage later today.

Last month during the House of Commons debate, Mrs Miller said: “Enabling same-sex couples to marry will in no way undermine those who believe… that marriage should be between a man and a woman, they can continue to believe that. That is their right.”

Several other amendments have been tabled for the bill, including a similar one from equal marriage critic Lord Dear, who proposed an amendment protecting those who believe marriage is “the union of one man and one woman for life to the exclusion of all others.”

An amendment tabled by MPs from both parties would mean that even if passed at all stages, the law would not come into effect until voters approved it at a referendum.

Yet 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.

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

The Marriage (Same Sex Couples) Bill comes back in committee 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.