The highest-profile party leader to date to warn PM David Cameron to change course on redefining marriage, according to the UK Telegraph:
Emma Pidding, whose organisation represents volunteers within the party, said she was concerned about the possible impact on the Tory election campaign if the plans for same-sex marriage go ahead.
The Government launched a consultation on the proposals earlier this year, and Mr Cameron was last week reported to have told gay groups he was determined to push the change through by the time of the election in 2015.
Ms Pidding today told BBC Radio 4's World At One: "My concern is that we are potentially upsetting our members and activists when I have one goal, and that is to obtain a Conservative majority government in 2015.
"Anything which upsets any of my members, I don't like to see that."
Ms Pidding said the issue of gay marriage was of passionate interest to "a few individuals" on either side of the argument but was not a priority for most Tories.
Conservative MP David Burrowes - a vocal critic of the proposals - said gay marriage was the kind of issue which might be a determining factor for a significant number of voters in crucial marginal seats, like his Enfield Southgate constituency in north London.
"The issue is one that is vote-defining for many people," Mr Burrowes told the programme. "Even in my constituency where they know that I am firmly opposed to the proposal, people say that if that does go through as legislation, then they won't vote for me.
"That must concern me and it concerns many other colleagues in marginal seats."