The Conservatives have reacted angrily to claims by two openly gay ministers that many Tory MPs are homophobic.
Culture Secretary Ben Bradshaw told the BBC News website: "a deep strain of homophobia still exists on the Conservative benches".
Foreign office minister Chris Bryant said: "If gays vote Tory they will rue the day very soon."
But Alan Duncan, one of two gay shadow cabinet ministers, accused the two men of "stirring up hatred and division".
Mr Duncan said: "This is the last gasp of Labour's desperation. Bradshaw and Bryant are simply trying to stir up hatred and division from the last century and it's both unwarranted and unworthy.
"It's simply untrue. I believed we had reached the happy point where politics had been taken out of this altogether. But these remarks show that Labour is actually the nasty party.
"I have publicly paid tribute to Tony Blair for his achievements, particularly on introducing civil partnerships. David Cameron this week said that on section 28 we had to admit we got it wrong. The party has changed. I bet in Labour backwaters there are plenty of people who don't like the fact that Ben Bradshaw is gay."
The Conservatives are keen to stress that their prospective general election candidates include a number of gay people, including party vice chairman Margot James, and that the next generation of Tory MPs will be more socially liberal in their attitudes than their predecessors.
In a survey of 144 prospective Parliamentary candidates in winnable seats for the ConservativeHome website, 62% say same sex couples should be given the same benefits as married couples, while 31% disagree.
Tory leader David Cameron this week apologised for Section 28, the controversial law brought in by the Conservatives in 1988 banning local authorities from portraying homosexuality in a positive light.
Mr Cameron, the first Tory leader to speak at a gay pride event, said: "I am sorry for Section 28. We got it wrong. It was an emotional issue. I hope you can forgive us."
His words were described as "historic" by Ben Summerskill, chief executive of gay rights campaign Stonewall, adding it would remove a major obstacle in the way of many of Britain's three million gay people voting Tory.
But Mr Bradshaw and Mr Bryant urged gay people to study Conservative voting records on issues such as gay adoption and hate crimes, which they say reveal a streak of homophobia.
In a joint statement with gay work and pensions minister Angela Eagle they said: "The Conservatives seem to have missed the point on this, yet again. David Cameron has apologised for his support of Section 28, but the argument has moved on.
"Why are the Conservatives rejecting important equality legislation for Lesbian, Gay, Bisexual and Transgender people in the shape of the Equality Bill? Why did Cameron and his frontbenchers oppose fertility rights for lesbians?"
They also questioned the stance of the Conservatives' new allies in the European Parliament.
"The reaction criticism like this provokes in the Conservative ranks shows they haven't changed on this. Cameron hasn't confronted his party on this issue and they should be judged on their actions, not their soft words."
And Commons leader Harriet Harman, whose Equalities Bill currently making its way through Parliament would outlaw discrimination on grounds of sexuality, urged people to disregard Mr Cameron's words on Section 28.
She told Pink News: "I don't think anyone should be fooled by the apology, which is already 25 years too late. It is not the view of the Tory party. They have voted against the Equality Bill. If they were sincere, they would support it."
And she backed the comments by Chris Bryant and Ben Bradshaw, saying: "The essential heart of the Tories is homophobic."
Prime Minister Gordon Brown, whose wife Sarah will be joining Saturday's Pride London event, sent a message to the organisers praising their campaign.
He said: "This government is committed to standing at your shoulder in the fight for equality and we are guided by one very simple principle when it comes to LBGT (Lesbian, Bisexual, Gay and Transgender) rights: you can't legislate for love."
It comes as new research suggests a rising number of gay people are planning to vote Conservative at the next election.
A membership survey by Jake, a networking group for gay professionals, found 38% would vote Conservative at the next election, 1% higher than the general population, according to an average of recent opinion polls.
Labour came third on 20% behind the Liberal Democrats - even though 86.6% of those surveyed said Labour was the party that had achieved most for gay people and just 4% said the Tories were "gay friendly", compared with 44% for Labour and the Lib Dems.
Jake surveyed 506 of its members anonymously on their voting intentions between 18 and 21 June and carried out a separate survey of 600 of its largely male membership on their general attitude towards the big three parties.