Susie Leafe, a prominent evangelical within the Church of England, has quit her role as director of the conservative campaign group Reform.
Chairman of Reform Mark Burkill told members in a message on Thursday it was 'with deep regret' that he announced Leafe's decision to resign.
Susie Leafe has been a prolific campaigner within the Church's hierarchy and has spoken consistently against women bishops and against same-sex marriage since her appointment as director in 2013.
In her letter of resignation she said: 'For the past six years it has been a joy to serve alongside faithful brothers and sisters, providing information and proclaiming the gospel.'
Christian Today approached Leafe as to why she resigned but she declined to comment.
Other members of the Reform Council, who lead the conservative pressure group within the Church, have also declined to comment on the reasons behind her resignation.
Mark Burkill said: 'We are very grateful for all she has contributed to Reform's ministry in this time and what has been achieved through her work. We look forward to working with her in contending for the gospel in whatever future ministry the Lord may call her to.'
Angus Macleay, Chairman of Reform Trustees, said: 'Susie has worked tirelessly on behalf of the Reform membership over the last six years, traveling up and down the country, preparing countless briefing papers for both the Reform Council and members. She has contended for the gospel in many ways, in particular on the floor of General Synod where she has shown admirable courage in standing for the truth. Her contribution to the work of Reform has been considerable and she will be greatly missed'.