With the first gay marriages in England and Wales just hours away, the head of Christian Concern has called on churches to uphold the distinctive beauty of God's pattern for marriage.
Andrea Minichiello Williams, also a member of the General Synod of the Church of England, said the last five decades of campaigning against the nuclear family had "obliterated" marriage, and that while the label remains "the substance has gone".
Gay marriage comes into law in England and Wales at midnight tonight and some same-sex couples have opted to say their vows seconds after the clock strikes midnight.
Ms Minichiello Williams was critical of the change: "God's blueprint for marriage and family has been ripped up by our society and every day we see and feel all around us, the huge emotional, economic and spiritual pain that results.
"The dismantling and destruction of marriage between one man and one woman for life, has produced a state marriage which is a mirage - an illusory reflection of the real thing."
She said the churches had a role to play in the new family landscape, demonstrating the distinctiveness of Christian marriage as a lifelong commitment that puts children first.
"The churches must hold out the distinctive beauty of God's pattern for marriage in order to review and renew real marriage which is God's gift to society," she said.
"The churches must not retreat but demonstrate that real marriage stands for life-long commitment whatever the cost; marriage that puts the welfare of children first; marriage that values the complementary roles of man and woman; marriage that reflects the self-sacrificial love of God.
"Christian marriage is much more than state marriage."