Church of England clergy who have "lost confidence" in the Bible and biblical ethics should resign or be removed, the head of Christian Concern has said.
Andrea Williams was responding to a survey of CofE priests by The Times that found over half (53%) support priests being allowed to conduct same-sex weddings if they wish. Just under half (49%) said they would personally be prepared to conduct them if rules were changed to permit them.
A majority (59%) said they plan to offer blessings to same-sex couples after proposals were backed by the General Synod in February.
The study also revealed widespread support for a change to the Church's current opposition to premarital sex (62%). Only around a third (34.6%) said the teaching should remain unchanged.
Nearly two thirds (64.5%) said that the Church should change its teaching that "homosexual practice is incompatible with scripture", and a similar proportion (63.3%) supported allowing gay priests to enter into civil partnerships.
Responding to the results of the study, Mrs Williams said the Church of England needed an "influx" of leaders committed to the Bible.
She warned that mirroring liberalising trends in society would lead the Church of England down a "road to extinction" as she called on the Church to be a voice for life-long heterosexual marriage.
Mrs Williams cited a recent study by Christian Concern which found that 61% of Church of England churches with the largest youth groups were those that supported the Church's historic doctrine on heterosexual marriage.
"To survive and thrive the Church of England needs leadership that believes the Bible and puts it into practice," she said.
"The Christian gospel has always offered a radically distinct, challenging and life-giving vision to society. Simply aping the current values of the culture around us is the road to extinction for the Church of England.
"Church leaders that have lost confidence in the Bible and the beauty of God's ethical teaching should resign or be removed.
"What the Church of England needs is an influx of leaders that believe that the gospel of Jesus remains the best news for society and who are able to present it and practice it in today's world."
She continued, "If the church wants to grow, attract youth, and remain relevant in society it needs to advocate for Biblical teaching on marriage and sexual ethics.
"The Church should not be adjusting its teaching to follow the culture or society, but proclaiming the benefits for society and individuals of life-long heterosexual marriage and reserving sexual expression for marriage."
Speaking to Premier Christian News about the survey, Anglican evangelical Dr Ian Paul suggested the problem lay with senior leaders.
"I think the Church of England is in a real mess because for many years, despite the fact that clergy stand up and make a public vow ... those responsible for training and ordaining the clergy simply don't hold them to account," he said.
"We are unable to say anything coherent to our culture as a Church ... because within the clergy, we don't agree on anything. We even have bishops who disagree with the doctrine of the Church."
He added, "Somebody once said 'A house divided against itself cannot stand', and unless we see some big changes in the church - unless we actually say we're going to take the doctrine of the Church seriously - I do think we're fatally wounded."