The deputy leader of the Liberal Democrats has said that gay couples are likely to gain full rights to marriage under the current Parliament. This would represent a revolution for gay rights, but there is still a long way to go before same-sex couples achieve full rights to marriage as they are arguably entitled to under human rights law.

Simon Hughes MP has told Yoosk.com, a question and answer website, that Liberal Democrat MPs would be consulted on the rights of gay couples. He said "I don't know the answer because we haven't had the discussion", but that "I see absolutely no reason why we shouldn't all be able to support what Nick Clegg said, which is that it would be appropriate in Britain in 2010-11 for there to be the ability to have civil marriage for straight people and gay people equally."

The human right to marry

If Mr Hughes' prediction is correct and the right to marry was granted to same-sex couples, it would represent the end of a long and tortuous road for campaigners. Article 12 of the European Convention on Human Rights provides:

Men and women of marriageable age have the right to marry and to found a family, according to the national laws governing the exercise of this right.

However, the UK has not yet chosen to extend this right to same-sex couples. The Civil Partnership Act 2004, passed under the previous government, went some of the way towards doing so by allowing same-sex couples to form civil partnerships. In fact, only same-sex couples are allowed to form civil partnerships in the UK, a restriction which a heterosexual couple have recently challenged in court.

Civil partnerships entitle couples to comparable rights as they would receive under civil marriage, for example in relation to property, tax and pensions. But although civil partnerships were a step forward, many still see them as inadequate and representative of a two-tier system. As a commentator on Pink News put it, they "were a fantastic milestone for gays and lesbians but it is clear now they are not good enough." It is reasonable for same-sex couples to ask why they are still denied access to the ancient institution, even if in name only; but from where is the change likely to arise?

One potential route to change is through a court challenge. Baroness Ruth Deech, the Chair of the Bar Standards Board and an expert on family law, recently questioned whether marriage rules are compatible with human rights law. She noted in a lecture at Gresham College that 33,956 civil partnerships had been registered since the 2004 Act – which came into force in 2005 – with men representing 53% of that number. But she went on to say:

The issue now is whether human rights legislation means that same-sex couples can require their unions to be entered into by marriage and be marriage. At the moment the prohibition remains – s. 11(c) of the Matrimonial Causes Act provides that a valid marriage can be entered into only by a male and a female. This might be said to be inconsistent with the articles of the Equality Bill that prohibit discrimination in areas of family and private life and between the sexes. If so, is it for the judges or for Parliament to take that final step for same-sex couples? The religious factions have fought successfully for their existing exemptions to be retained in the Equality Bill 2010, in order that they may make choices determined by faith in employment and services offered.

Indeed, the courts have in recent times sought to enforce gay rights. As Lord Rodger said in a recent Supreme Court judgment, which criticised the Government's policy of sending back gay asylum seekers to states where they would be persecuted, "gay men are to be as free as their straight equivalents in the society concerned to live their lives in the way that is natural to them as gay men" (he also painted an interesting picture of gay life in Britain involving Kylie concerts and exotic cocktails).

It is unlikely, however, that judges can be relied upon to step up on this issue in light of the recent judgment of the European Court of Human Rights in Schalk and Kopf v. Austria, a decision which the UK expressly backed. The Strasbourg court rejected the applicants' argument that Austria's refusal to grant same-sex marriages represented a breach of their human rights. It observed that among the Council of Europe states there was little or no consensus on same-sex marriage, and that this was therefore a matter for the national authorities who were best placed to assess and respond to the needs of society in this field. Clearly, the European Court of Human Rights considers that gay marriage falls within the 'margin of appreciation' which states sometimes have to set their own policy agenda in relation to controversial social issues.

Even if a challenge to the existing law on human rights grounds did succeed in the UK courts, the government would not be bound to change the law. On a controversial issue such as gay marriage, the backing of Parliament will be essential to change the status quo; in any case the Supreme Court in particular is unlikely to be willing to place itself in the political limelight as its US equivalent has done by making controversial decisions on social issues.

The will of Parliament

So will Parliament, and specifically the coalition government, seek to alter the law? Simon Hughes' comments certainly suggest that change is imminent. However, a roadblock to reform may ultimately come from religious authorities, many of whom are against full gay marriage. One important concession which the 2004 civil partnership legislation made to religious authorities was that ceremonies could not take place on religious premises.

However, religious authorities have nowhere near the influence they have in other jurisdictions such as in the United States, as evidenced by the fact that the religious premises restriction has recently been removed by an amendment to the Equality Act 2010. Lynne Featherstone, the Equalities minister, has said in an answer to a Parliamentary question that gay couples could now use "religious readings, music and symbols" in civil partnership ceremonies, further dissolving the already tenuous distinction between civil marriage and civil partnerships.

The coalition government is clearly concerned over the reaction to potential reforms from the religious community, and is seeking to involve them in any future decisions. It has recently announced a consultation with "those with a key interest in this issue about what the next stage should be for civil partnerships, including how some religious organisations can allow same-sex couples the opportunity to register their relationship in a religious setting if they wish to do so."

To that end, Simon Hughes was keen to make clear that religious communities would not be forced to accept gay marriage, stating that the civil law "is different of course from faith ceremonies which are matters for the faith communities – for the Christian Church or the Muslim community – and they have to decide what recognition they want to give." But the terms of the consultation seem to imply that the government is not seeking the opinion of religious groups as to whether to institute the changes; rather, it is trying to persuade them to come along for the ride.

Given that marriage law in the UK is purely a civil institution, if the government chooses to go ahead with granting same-sex couples full marriage rights, there will be little in practice that religious authorities could do to prevent this significant upgrade in rights. And with public opinion softening after five years of civil partnerships with no apocalyptic results, it is possible that the time for gay marriage in the UK might finally have come.