Contrary to reports, gay marriage is one policy on which David Cameron has not changed course. There was never any intention to include legis­lation in the Queen’s Speech last month, which pre-dated the end of the government’s consul­tation. Now, the consultation has ended and the coalition has pledged to legislate before 2015.

There are strong political reasons for Mr Cameron’s commitment to the policy. He is determined for his government to be remembered for more than austerity and has also argued persuasively that same-sex marriage can be reconciled with Conservative philosophy. If marriage, as Conservatives believe, is the foundation of a successful society, then it should surely be offered to the greatest number of people possible. Mr Cameron says he doesn’t support gay marriage in spite of being a Conservative but because he is one.

On this issue, the Prime Minister is right. The value of marriage would be increased, not diminished, through its extension to same-sex couples. Some may question whether the introduction of gay marriage is necessary when the Civil Partnership Act 2004 already allows couples access to almost all of the legal rights enjoyed by heterosexuals. Yet this two-tier system implicitly condones the belief that same-sex relationships are inferior to others. Gay couples are rightly aggrieved that they are unable legally to refer to themselves as “married”. Nor is the distinction merely a semantic one: while a civil marriage is formed when the couple exchange spoken words, a civil partnership is, rather less romantically, formed when the second civil partner signs the register.

Long before its consultation began, the government indicated that no religious organisation would be forced to conduct same-sex marriages. The principle of religious freedom demands as much. Indeed, it went further by ruling that those religious groups that wish to officiate gay marriages, such as Reform Jews and Quakers, would be barred from doing so, even though they can now legally host civil part­nerships. This has not prevented a series of absurd responses from senior clerics. Cardinal Keith O’Brien, the leader of the Catholic Church in Scotland, has compared the introduction of gay marriage to the legalisation of slavery. The Archbishop of York, John Sentamu, has accused Mr Cameron of behaving like a “dictator”. Now, in its formal submission to the government’s consultation, the Church of England has reaffirmed its opposition to gay marriage on the basis that it would “alter the intrinsic nature of a marriage as the union of a man and woman, as enshrined in human institutions through history”. For a church that was founded in opposition to the belief that a sacramental marriage could never be dissolved, it is a reactionary stance.

A greater challenge for liberals is the Church’s assertion that European human rights law could force it to hold gay marriages, with some even raising the spectre of disestablishment. Such a ruling would require the government to adjudicate between the competing priorities of religious freedom and equality. The Home Office’s lawyers insist that the law favours the former, while independent observers suggest that, at most, religious organisations would be permitted to conduct gay marriages voluntarily. The suspicion arises that the Church’s claims are part of a desperate rearguard action, aimed at preventing same-sex marriage ever reaching the statute book. Many in Mr Cameron’s party will prove similarly obstructive but the Prime Minister should use the full weight of his office to override their dissent.

When the Civil Partnership Act was passed, it was said that no single law had done more to promote human happiness. In the same spirit, gay couples should be granted full equality.