Same-sex marriage is an idea whose time has come. It is the growing trend all over the world, from Canada to South Africa and Argentina.

Why can’t we have marriage equality in Britain too?

Political support for ending the ban on gay marriage is growing rapidly. London mayor Boris Johnson and Conservative MP and former party vice-chair Margot James have both come out in favour of allowing lesbian and gay couples to marry in a registry office, on the same terms as heterosexual partners.

This view is also endorsed by the leader and the deputy leader of the Liberal Democrats, Nick Clegg and Simon Hughes. Indeed, Hughes has predicted that the ban on same-sex marriage will go within five years.

All five Labour leadership contenders – Ed Balls, Diane Abbott, Andy Burnham, Ed Miliband and David Miliband – now back marriage equality, regardless of sexual orientation.

Public attitudes have also shifted strongly in favour of allowing gay couples 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.

Some people say that civil partnerships are sufficient for gay couples. This is hypocritical. They would not accept a similar ban on black people getting married.

They would never agree with a law that required black couples to register their relationships through a separate system called civil partnerships.

It would be racist to have separate laws for black and white couples. We’d call it apartheid, like what used to exist in South Africa. Well, black people are not banned from marriage but lesbian and gay couples are.

We are fobbed off with second class civil partnerships.

Personally, I don’t like marriage. I share the feminist critique of its history of sexism and patriarchy. I would not want to get married. But as a democrat and human rights defender, I support the right of others to marry, if they wish.

That’s why I believe that civil marriage in a registry office should be open to everyone without discrimination.

Don’t get me wrong, civil partnerships are an important advance. They remedy many – though not all – of the injustices that used to be experienced by lesbian and gay couples. But they are not equality.

They are discrimination. Separate is not equal.

In terms of the law, civil partnerships are a form of sexual apartheid. They create a two-tier system of partnership recognition: one law for heterosexuals (civil marriage) and another law for same-sex couples (civil partnerships).

This perpetuates and extends discrimination. The homophobia of the ban on same-sex civil marriage is now compounded by the heterophobia of the ban on opposite-sex civil partnerships.

Just as a gay couple cannot have a civil marriage, a straight couple cannot have a civil partnership. Two wrongs don’t make a right.

Sadly, the official policies of the Conservative and Labour parties do not support same-sex civil marriage. They oppose it. They support discrimination.

The Green Party and the Liberal Democrats are, so far, the only parties officially committed to giving same-sex partners the right to civil marriage – and heterosexual couples the right to civil partnerships.

In a democracy, we are all supposed to be equal under the law. The Con-Lib coalition’s professed commitment to gay equality cannot be taken seriously while it upholds the ban on same-sex marriage. Over to you, Dave and Nick.

This article was first published in Government Gazette