Leading article: Leaders of the gay revolution

Still nearly a year to go to the next election, and the heat of partisan competition is already intense. Not just in the sterile exchanges in the House of Commons over public-spending plans, but in the speed with which a party-political spat blew up last week over the issue of gay rights. The fuss began when Gordon Brown and David Cameron competed to show off their liberal credentials during Pride Week. The Prime Minister did not actually attend the London march, but his wife did, and he sent a message extolling the Labour Government's record in legislating for gay equality. Meanwhile, the Leader of the Opposition apologised to Pink Paper, the online gay newspaper, for his past support for the notorious "Section 28" – the symbolic law that banned the "promotion" of homosexuality.

This provoked Ben Bradshaw, the Secretary of State for Culture, to say: "A deep strain of homophobia still exists on the Conservative benches." Yesterday Angela Eagle, the pensions minister, and Alan Duncan, the shadow Leader of the House of Commons, traded insults and claims about each party's respective voting records on gay rights. Mr Duncan pleaded: "Get the politics out of this."

No chance. Instead, our aim should be to try to clear away the party-political distortions, because, as with the row over taxes and spending, there are differences between the two main parties on gay equality.

First, we should acknowledge the Government's record. The evolution of Britain as a society at ease with openly gay people is a significant achievement. Nick Clegg, the leader of the Liberal Democrats, astutely said on a Labour-supporting website yesterday that "a lot has been accomplished". Section 28 has been repealed; the age of consent has been equalised; the law against discrimination has been strengthened; above all, civil partnerships represent a huge step towards full legal equality.

Second, we should acknowledge the importance of David Cameron's conversion. The Tory leader is rightly proud that he got a Conservative Party conference to applaud gay marriage three years ago. Nor should his apology for Section 28 be brushed aside as mere positioning. It matters because it ensures that the social revolution of the past 12 years cannot be rolled back.

In both Mr Brown and Mr Cameron's cases, it is possible to cavil. Mr Brown has not been brave or principled in his support for gay rights. As far as we can tell, he has never taken part in votes in the House of Commons to promote equality for gay people. Nor is Mr Cameron quite as radical as he pretends. Tory representatives may have clapped when he said that "marriage is a vital institution", adding: "It means something whether you're a man and a woman, or a woman and a woman, or a man and another man." But he was talking of civil partnerships, rather than gay marriage as such. Gay marriage, advocated by Peter Tatchell, the perpetual campaigner, is supported only by the Liberal Democrats.

Both Labour's record and Mr Cameron's conversion are relevant in judging which party is more likely to maintain the forward momentum of this great social change.

It is in this respect that Mr Cameron, or rather his party, is suspect. The evidence for this is not the Conservative Party's new alliance in the European Parliament. The new group is embarrassing because it puts the Tories on the fringes of European politics, not because some of its members are a bit odd. There is an air of electioneering artifice in Labour's attempt to embarrass Mr Cameron by citing the homophobic past of the Polish Law and Justice Party. "They do believe in equal rights and they have made that very clear," Mr Cameron said.

No, Mr Cameron's problem is not the Poles; it is his own back benches. They are still full of MPs for whom the transformation of the past 12 years is a matter of profound regret. Even the expenses-driven clear-out is unlikely to shift the composition of the parliamentary Tory party much. There is a tension at the party's heart; witness Mr Cameron's initiative on family values on which we report today. To that extent, the charge laid by Mr Bradshaw and Ms Eagle must be upheld: the Tory conversion on gay rights is nothing like as thorough as the leader and a few of his allies would like.

Labour has the edge, therefore. But, because the Conservatives are unlikely to reverse the gains already made, how much this matters depends on how much more of the social revolution you think there is to be completed.