The battle against gay marriage causes deep divisions in politics and religion

The Pope's representative in Britain has urged Roman Catholic leaders to form a united front with their Muslim and Jewish counterparts in his Church's latest attempt to prevent gay marriage.

The Catholic Church's position is causing ever-deeper rifts among its followers and in the Tory party. The most senior Catholic in the British Government, Work and Pensions Secretary Iain Duncan Smith, has confirmed that he supports gay marriage. However, another senior Catholic, Tory Chief Whip, Patrick McLoughlin, has privately told Tory backbenchers that current proposals will "not come to a vote," and that they will be "kicked into the long grass" according to the Mail on Sunday.

It is not just in the UK that this schism is appearing. A survey by the Pew Research Centre has found that opposition to gay marriage in America is shrinking, even among Catholics.

The Catholic campaign in Scotland has been particularly venomous. The Catholic Education Commission there has said that Scottish Government proposals will make it impossible for teachers in denominational schools to teach according to church doctrines. Michael McGrath, director of the Scottish Catholic Education Service said: "This understanding of the sanctity of marriage is divinely ordained in Church doctrine and underpins the teaching of marriage in Catholic schools across the world."

Following a letter from the Scottish Catholic Church to 100,000 Scottish Catholics, Scotland for Marriage is now planning to leaflet every house in Glasgow (some 300,000 homes) and is gathering a petition. Signatories include Britain's most senior Roman Catholic, Cardinal Keith O'Brien, and the former SNP leader Gordon Wilson. The group, backed by organisations including the Catholic Bishops' Conference of Scotland, the Christian Institute, the Evangelical Alliance and Destiny Churches, said it also planned to use mobile advertising vans to put across its opposition to same-sex weddings.

Also in Scotland, the Council of Glasgow Imams recently agreed a joint resolution describing same-sex marriage as an "attack" on their faith and fundamental beliefs.

On the other side of the Scottish battle lines, the United Reformed Church, the Quakers, Buddhists and the Pagan Federation among others have started the Faith in Marriage campaign. They will hand over an open letter to MSPs at Holyrood demanding the right to conduct same-sex marriages.

Rev Scott McKenna, Church of Scotland minister for Mayfield Salisbury Parish in Edinburgh, said: "In opposing equality, churches reinforce homophobia in society and that can lead to pain, low self-respect and, in some cases, violence. In the end this is about people who are on the receiving end of prejudice and are suffering because of that. The cycle needs to be broken."

It is also becoming increasingly clear that the Catholic Church does not represent its followers in the UK. When it sent a letter to all priests to read out at mass, many parishioners walked out and some priests refused to read it. When the Catholic Education Service sent a letter to Catholic schools asking pupils to sign a petition against gay marriage, some pupils objected to this possible breach of equality law and inappropriate promotion of political views, as we reported. Catholic Voices has now accused the NSS of being 'sinister and illogical' in our challenge to the Catholic Education Service.

A statement on their website said that the NSS 'have to argue that (a) the argument in favour of gay marriage is an argument in favour of equality; (b) those who oppose gay marriage are therefore against equality; (c) because schools are committed in law to upholding equality, therefore schools speaking against gay marriage are breaking the law. The logic falls at the first hurdle, because: there is no right to same-sex marriage, and therefore no discrimination'.

They don't seem to understand what equalities are about. Women once had no right to vote so according to Catholic Voices' argument, they were not discriminated against. Equality means giving a right to a group that is denied it for no good reason.

As cheerleaders for the Catholic Church we would expect Catholic Voices to support attempts to inculcate young people with political Catholicism, but it is for the Secretary of State to decide whether that is appropriate in state funded schools - and according to the law, it is not.

As well as dividing believers and politicians, the battle has other casualties - free speech for one. A Christian who was demoted for his views on gay marriage tried to use human rights as a defence in his legal case against his employer but District Judge Charles Khan at Manchester County Court disallowed this argument. Adrian Smith, a housing manager at Trafford Housing Trust, commented on Facebook that gay marriage would be 'an equality too far'.

Smith's legal case against his employer's breach of contract can continue but the judge's ruling means that he cannot rely on the human rights argument. The Trust disciplined him because it was worried about its reputation in relation to its public function of providing social housing but gay rights campaigner Peter Tatchell has offered to appear as a witness in his defence.