The Christian Institute has dismissed calls for a change to the Church of England's position on marriage after a poll claimed broad support among Anglicans.
The YouGov survey found that nearly half (48%) of people who identify as Anglicans in England believe that same-sex marriage is "right".
The survey was conducted on behalf of the Ozanne Foundation, which is campaigning for LGBT equality in the Church of England.
Responding to the results, the organisation's founder Jayne Ozanne said they showed "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".
Colin Hart, director of the Christian Institute, however, said that Christian doctrine should not be determined by public opinion.
"You can't abandon Christian teaching because some people don't like it," he said.
"The faith once delivered to all the saints didn't emerge as a result of polling or focus groups. Neither will it emerge from following secular trends.
"The Bible's message is clear. Marriage can only ever be between one man and one woman, to the exclusion of all others, for life."
YouGov last month polled 1,171 adults in England who described themselves as Church of England, Anglican or Episcopal. The survey did not ask them whether they attended church.
Mr Hart added: "We cannot draw any conclusions from the poll about the beliefs of communicant members of the CofE."
The poll was conducted after the House of Bishops issued a statement saying that sex should only take place within the context of marriage.
The statement was intended as a response to the introduction of heterosexual civil partnerships by the Government.
"Sexual relationships outside heterosexual marriage are regarded as falling short of God's purposes for human beings," the statement said.