Nearly half of self-identifying Anglicans in England support same-sex marriage, according to a poll.
YouGov asked over 5,000 people across the UK whether they believed same-sex marriage to be right or wrong.
Of the 1,171 people surveyed in England who identified as Church of England, Anglican or Episcopal, 48% said that same-sex marriage was right, contrasting with around a third (34%) who said it was wrong and 18% who answered "don't know".
The poll did not ask about church attendance.
When YouGov first asked the question in 2013, 38% of self-identifying Anglicans said that same-sex marriage was right. That figure rose to 45% in 2016.
The 2020 poll found that they are still less likely than the rest of the population to support same-sex marriage, with 60 per cent of total respondents believing same-sex marriage to be right. Support within the wider general public has also risen from 46% in 2016.
Londoners were more likely to support same-sex marriage (68%), as were those aged 18- to 24 (74% vs 37% of 65+).
The latest poll was conducted on behalf of the Ozanne Foundation, which is campaigning for LGBT equality in the Church of England.
The foundation's director, Jayne Ozanne said: "These results show that those opposed to same-sex marriage are now clearly in the minority, and that a substantial group within the Church of England believe same sex marriage is right.
"This shows the urgent need for the Church of England hierarchy to recognise and respect the clear views of a significant proportion of its members, which are steadily increasing as time goes by."
The Bishop of Liverpool and chair of the Ozanne Foundation, the Rt Rev Paul Bayes said: "These results provide a challenge to us in leadership within the Church of England to ensure that we understand the views of the people we serve.
"Attitudes are indeed changing quickly, and we must be open to what the Holy Spirit is saying to us through them if we are to be an effective witness of God's love to the nation."
Others in the Church of England were more sceptical of the findings. Peter Ould, Church of England priest and commentator on sexual identity, said that self-declared Anglicans should not be conflated with active members of the Church of England.
He accused Ozanne of using a "manipulative" definition of 'Anglican' "which doesn't reflect the actual members in the pews".
"If all of these 'Anglicans' were actually attending church there would be well over 10 million people worshipping in the Church of England every Sunday!" he said.
He added: "On top of this, the change in support from the last survey is well within the margin of error, meaning there is no statistical significance in the claimed increase in support for same-sex marriage."
Church of England minister Liam Beadle tweeted: "I'm not sure what this is meant to demonstrate. We don't do theology by opinion poll. Indeed, my opinion and the Church's teaching can be in tension without my wanting any doctrinal revision!"
Matthew Mason, tutor in ethics at the Pastors' Academy, posted a similar comment on Twitter: "This would only be remotely interesting or relevant if you gave a clear definition of what respondents mean by 'Anglican' - my father worked in prisons for a couple of decades, and almost everyone self-identified as CofE, and also revealed the questions you asked."