New York’s legalisation of gay marriage is symptomatic of a global trend. From South Africa to Canada, Argentina, Portugal and beyond, same-sex marriage is becoming a fact of life and law.

Marriage equality is now the focus of many lesbian, gay, bisexual and transgender (LGBT) campaigns worldwide. It is fast becoming the litmus test in the battle for equality.

How ironic. At the very moment that heterosexual couples are deserting marriage in droves, lesbian and gay couples are rushing to embrace it.

Straight partners are falling out of love with matrimony. Provisional statistics for England and Wales show that the number of marriages in 2009 was the lowest since they were first calculated in 1862.

Far from weakening or undermining marriage, as homophobes claim, many same-sex couples seem hell-bent on shoring up an institution that is, for many heterosexuals, failing, discredited and irrelevant.

While the push for same-sex marriage is an issue of equality, which I support, it also signifies the rising conservatism of the LGBT community and a loss of radical vision. It reeks of assimilationism and conformism with the straight status quo.

As we celebrated Gay Pride in London on Saturday, with calls for marriage equality, the sceptical, questioning attitudes of the early lesbian and gay liberation pioneers were almost entirely absent.

Marriage has a long history of sexism and patriarchy; being originally devised to ensure the male sexual control of women and the inheritance of property through the male line, from father to son. Even the language of marriage is misogynistic. An alternative meaning for the word husband is ‘to manage’, which sums up the relationship between men and women in many marriages, past and present. Traditionally, the father of the bride gives away his daughter to her husband-to-be, symbolising the passing of women from one man to another. For all these reasons, I am not a great fan of marriage.

Indeed, I have proposed a new, more egalitarian and flexible system of relationship recognition and rights – what I have called a Civil Commitment Pact (CCP).

Under this CCP system, which seeks to recognise all relationships of mutual care and commitment, an individual could nominate any ‘significant other’ person in their life as their next of kin and beneficiary. In the case of a couple, they would be able to select from a menu of rights and responsibilities to create a CCP that is tailor-made to their particular circumstances and needs; thereby accommodating the wide range and diversity of modern relationships.

Speaking personally, I would not want to get married. I agree with the feminist critique. However, as a human rights campaigner, I strongly and actively defend the right of others to marry, if they wish.

Moreover, the ban on same-sex marriage is homophobic discrimination. All discrimination is wrong and should be opposed. Since marriage exists, it ought to be open to everyone.

For these reasons, despite my reservations about the institution of marriage, I am coordinating the Equal Love campaign, which seeks to end sexual orientation discrimination in both civil marriage and civil partnership law. It is a simple issue: equality for all.

Under current UK legislation, gay couples are banned from civil marriages and heterosexual couples are banned from civil partnerships. The homophobia of the ban on same-sex civil marriages is compounded by the heterophobia of the ban on opposite-sex civil partnerships. Two wrongs don’t make a right. Arbitrarily excluding straight couples from civil partnerships is just as reprehensible as denying gay partners access to civil marriage.

Imagine the outcry if the government banned black couples from getting married and offered them civil partnerships instead. Most people would condemn separate laws for black and white people as racism and apartheid, like the legislation that once existed in South Africa.

Well, in Britain today, black couples are not banned from marriage but gay couples are. Legally, this is a form of sexual apartheid – one law for gay couples and another law for heterosexual partners. In a democratic society, we should all be equal before the law.

To challenge this discrimination, eight British couples – four gay and four heterosexual – filed a joint legal application to the European Court of Human Rights on February 2nd, seeking to overturn the twin bans on gay civil marriages and heterosexual civil partnerships.

We are confident that the European Court will eventually rule in our favour. But we’d much prefer the government to bring forward legislation of its own free will, to put right an obvious inequality.

The British people are ready for change, with a clear majority in favour of allowing same-sex partners to marry. A Populus poll for the Times newspaper in June 2009 found that 61 per cent of the public believe that: “Gay couples should have an equal right to get married, not just to have civil partnerships.” Only 33 per cent disagreed.

The deputy Prime Minister Nick Clegg and London Mayor Boris Johnson back marriage equality, as do the leaders of Labour and the Greens, respectively Ed Miliband and Caroline Lucas. Only David Cameron is holding out against same-sex marriage rights. What is he afraid of?