A survey of Tory constituency chairman has found the majority believe the UK Prime Minister David Cameron should abandon gay marriage.
It found 71% should drop the law, while nearly half say local parties have lost members as a result of the plans.
Only 3% say they have gained membership since the Conservative and Liberal Democrat coalition government announced the law, which is planned to take effect by 2015.
Anti-gay campaigners from the Coalition for Marriage conducted the poll, and it found over seven in 10 grassroots members believed gay marriage had damaged the Prime Minister’s standing in the party.
Colin Hart, campaign director of the campaign group, said: ‘What this latest poll reflects is the growing unease amongst grassroot Conservatives about the way the PM is trying to force through this policy without any electoral mandate and without any acknowledgment of the profound consequences this chance will have.’
He added: ‘If the PM continues to press ahead with this deeply unpopular, radical and profoundly undemocratic proposal, then he can expect to pay the price for this at the ballot box.’
UK-based gay rights charity Stonewall has also conducted a recent opinion poll through government organization YouGov on equal marriage. The poll returned 84% of 1,704 Britons under 30 support the plan.
The poll found 43% of 2,005 people believed marriage should be defined as between a man and a woman, while 43% said it should be between two people of any gender.
Ruth Hunt, Stonewall’s director of public affairs added: ‘We’re determined that same sex marriage won’t turn into another tuition fees issue, announced with much fanfare and then quietly dropped.
‘We trust the understandably high volume of responses to the government’s recent consultation won’t be used as an excuse for shunting the issue towards the end of this parliament.’
In August, Cameron said he was ‘absolutely determined’ the government would legislate for gay marriage in this parliament term.
The Coalition for Marriage survey, conducted by ComRes, asked a random sample of only 100 Conservative Party chairmen between 14 September and 2 October 2012.