The Queen's minister has warned that the appointment of his friend and protégé as the Church of Scotland’s first openly gay clergyman would lead to an “apocalyptic” split in the Kirk.

Rev Kenneth MacKenzie, the minister at Crathie Kirk, near Balmoral, said he had known Rev Scott Rennie for 25 years and believed him to be a “gifted and compassionate” man.

But he said Rennie’s appointment threatened the biggest split since 1843, when more than 450 ministers broke away to form the Free Church.

MacKenzie said he was dis-appointed Rennie’s sexuality had become an issue following his appointment as minister of Queen’s Cross church in Aberdeen.

Rennie, 37, who plans to move his partner into the manse, has the support of the local congregation but his appointment has been challenged by a group of protesters. The group raised the issue with the Kirk commission, which has now referred it to the general assembly, which will rule on the case later this month.

Almost a third of ministers and 8,500 of their supporters have voiced their opposition via an online petition organised by the Fellowship of Confessing Churches, an evangelical group.

MacKenzie said the row over Rennie’s sexuality represented a decisive moment for the church to reassert its attitude to marriage and define how ministers are expected to conduct their private lives.

“I believe that we are approaching a critical moment for the Church of Scotland and indeed for those denominations currently associated with it,” he said.

“To my mind, there will be no winners here. If the decision goes in favour of the \, many people will be very unhappy and Scott’s position within the church will be very difficult. But, for the most part, life in the church will go on pretty much as normal. If the decision goes the way of the Presbytery of Aberdeen, a number of people will be ecstatic, but I fear it may prove to be a hollow victory.

“Life in the church will never be the same again and my fear is that a sizeable minority of the clergy, and perhaps a majority of its people, may consider leaving the church, causing a rift felt in every parish.”

MacKenzie added: “There are, among \ closest friends, a good number of people who, though wanting the very best for Scott . . . will not support any proposal that the Church of Scotland should amend or dispose of its age-old standards when it comes to affirming marriage, or appointing parish ministers. I am one such friend.”

Rennie, a divorced father of one, was appointed as minister at Queen’s Cross in January with the congregation’s backing. However, the move was blocked following a complaint from about 12 dissenting members of Aberdeen Presbytery on the grounds that they objected to his lifestyle.

In March, a committee refused to back Rennie’s appeal and passed the matter to the General Assembly.

Conservative members want the Kirk to take a stand on the wider issue of homosexual clergy and have lodged a motion urging the church not to “train, ordain, admit, readmit, induct or introduce to any ministry of the church anyone involved in a sexual relationship outside of marriage between a man and woman”.

Last week, commenting on the row publicly for the first time, Rennie said he was surprised by the ferocity of the backlash against his appointment. He has lived happily with his partner, David, since divorcing Ruth, his ex-wife.

“Having lived happily with my partner in Brechin, getting on with parish life and all that entails, I did not imagine, given how peaceable and happy my time there has been, that such a furore would be caused following my desire to respond to God’s call by moving church,” he said.

The links between the royal family and Crathie are long-standing. In 1992 the Princess Royal married Timothy Laurence at the church.

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