A broad alliance of faith groups has released an open letter, sent to all Members of Scottish Parliament (MSPs), demanding the right to conduct marriages for same-sex couples, while an anti-equality group has said it will send a leaflet to every house in Glasgow, campaigning against marriage equality, ahead of Thursday’s council election.

The alliance, called Faith in Marriage, include members of the United Reformed Church, the Quakers, the Unitarians, Buddhists, the Pagan Federation, Liberal Judaism, the Iona Community, the Open Episcopal Church, and the Metropolitan Community Church. The alliance said that the current civil partnership scheme was not enough, was discriminatory, and therefore “an unacceptable infringement by the state on our freedom of religion and belief.”

The coalition has been formed as a response to the anti-equality Scotland for Marriage, which is composed of the Catholic Bishops’ Conference of Scotland, the Christian Institute, the Evangelical Alliance and Destiny Churches. Although not a part of this group, the Church of Scotland is also against gender-neutral marriage. Scotland for Marriage said it would send leaflet to every household in Glasgow against the proposals, at a cost of £15,000.

The anti-equality group also said that it would use mobile advertising vans to put across its opposition to gender-neutral marriage.

The Scottish government, after the conclusion of a 14-week consultation on the issue, said, according to the BBC, that it “tends towards the view” that same-sex couples should be able to have civil marriages.

The open letter, addressed to the MSPs, said that it would “strongly oppose” any attempt at keeping equal marriages outside the realms of religious venues. Indeed, the letter goes so far as to seek assurance from MSPs that any proposed legislation would “protect and extend” religious liberties by “giving those religious and humanist bodies that do want to conduct same-sex marriage the right to do so.”

The letter adds: “We respect the religious freedom of those bodies that currently do not wish to conduct same-sex marriages, and we agree that there should be a mechanism in place to ensure that they do not have to. This is a position widely supported by equal marriage campaigners.

“We do, however, note with dismay that little mention has been made by politicians or the media of the rights of those religious and humanist bodies that do wish to conduct same-sex marriages.

“We are concerned that this debate is being framed by some as ‘LGBT people vs religion’, when in reality there are many LGBT people of faith and there is a great divergence of opinion on same-sex marriage amongst – and within – religious bodies.”

This letter contrasts strongly with that of Cardinal Keith O’Brien, the most senior Catholic in Britain, who has said equal marriage is ‘a grotesque subversion of a universally accepted human right,’ a ‘madness’ pushed by ‘a disingenuous government.’

The Scottish government is still considering the responses it received to the public consultation, and has said it would not force faith groups to solemnise same-sex weddings.

In January, leaders of the Scottish Labour, Liberal Democrat, Green and Conservative parties signed up at an event in Holyrood to support equal marriage.