Mr Osborne said it had been a "good, constructive" meeting
The Tories would be "very happy" to consider same-sex marriage if elected, George Osborne has told gay activists.
The shadow chancellor met gay rights leaders including Peter Tatchell ahead of a protest outside Conservative campaign HQ by equality campaigners.
Mr Osborne said the modern Tories had changed, and "we have real policies to advance equality".
But Mr Tatchell said later that a commitment simply to consider the case for reform was "meaningless".
Civil partnerships give gays and lesbians the right to the same legal treatment across a range of matters as married couples.
But the government stopped short of referring to such unions as marriages when the Civil Partnerships Act was passed in 2004.
'Lacking in sparkle'
About 200 campaigners converged on Conservative headquarters in protest at remarks by shadow home secretary Chris Grayling, who last week sparked a row when he said people who ran bed and breakfast in their homes should "have the right" to turn away gay couples.
Mr Osborne was joined by shadow environment secretary Nick Herbert and shadow work and pensions secretary Theresa May when they met Mr Tatchell and fellow gay rights campaigners Tamsin Omond and Deborah Grayson.
Demonstrators protested over remarks by the shadow home secretary
Speaking afterwards, Mr Tatchell said he was disappointed that there had been no "concrete promises" from Mr Osborne, and that the shadow chancellor had refused to back and end to the ban on gay men donating blood.
He said: "The Tories are obviously worried that Chris Grayling's comments in support of homophobic discrimination by B&B owners have undermined their party's image as being gay-friendly.
"We only got this meeting with George Osborne because of the planned protest and because of the anti-Tory backlash generated by Mr Grayling's support for discrimination."
Mr Osborne said it had been a "good, constructive" meeting.
A Conservative spokesman confirmed that Mr Osborne had told Mr Tatchell: "David Cameron and I are very happy to consider the case for gay marriage."
Ms Omond said she still wanted to know what the Conservatives would do for lesbian, gay, bisexual and transgender people.
She added: "We fear that in private many top Tories still don't believe in full gay equality."
But Mr Herbert, who is in a civil partnership, said it had been a "good" meeting.
He said he recognised that some people "might have got the wrong impression" about the Conservatives, but "we have made huge changes as a party".
The meeting came after Mr Cameron gave an interview in the Sunday Telegraph in which he said he would govern for "everyone in Britain".
Mr Cameron said he would steer away the more "divisive" policies linked with the Thatcher governments of the 1980s, and urged the country to "join together, act decisively and move forward with optimism".
On Saturday, Mr Cameron said the Tories would change the law so that convictions for consensual gay sex with over-16s would not show up on criminal record checks.