Despite vocal opposition to David Cameron’s plan to allow same-sex couples to marry from the leaders of almost all the major faith groups, the faithful are just as likely to support it quietly as oppose it, the survey found.
And when those who actively describe themselves as religious but do not attend services regularly are included, more Roman Catholics and Anglicans back the redefinition of marriage than oppose it, it suggests.
Notably, the polling found that within most religious groups there are also minorities who believe that same-sex marriage is wrong but still think that it should be allowed.
The findings emerge from a survey of more than 4,000 people, commissioned by the organisers of the regular Westminster Faith Debates.
People were asked not only whether they identified with a religion or denomination but whether they looked to their faith or its leaders for guidance rather than their own instincts.
The polling, carried out by YouGov, found that opposition to gay marriage was strongest among those with the strongest religious convictions.
But overall, 43 per cent oft those who identified personally with a religion or denomination said they supported gay marriage, the same proportion as opposed it.
Among Roman Catholics, 44 per cent were in favour and 41 per cent against while among Anglicans support ran as 44 per cent against 43 per cent.
Even when those who say they do not attend services regularly are excluded, only 47 per cent of Anglicans churchgoers are opposed, with 40 per cent of regular attenders in favour.
Among Catholics, 48 per cent of regular massgoers are opposed to gay marriage with 42 per cent in favour.
Prof Linda Woodhead, of the Religion and Society Programme, an academic unit based at Lancaster University which organises the Faith Debates, said: “Given that the churches have really pulled out the big guns and made this the big issue that they are going to stand on, it is surprising that not even half of active churchgoers are opposed.
“The other interesting finding for me is that this identifies what I call the ‘moral minority’ in this country."
The poll showed that almost one in 10 people, of different religious persuasions, identified themselves as having a strong faith and looking to God, religious leaders or their teaching for guidance ahead of their “own reason” or “intuition”.
Prof Woodhead added: “We find them in all religions yet they are really similar to each other.
“The most striking thing about them is their attitude to personal morality and I think that is a new thing - it is like a moral protest group which belongs to our particular time.
“The majority of the population probably held a lot of their views 50 years ago but now they exist not as a relaxed majority but as a vocal minority who see themselves as standing against the majority.
“All the action is between them and the atheists – they bring themselves into existence they feed on each other.”