St Thomas' is the latest evangelical parish to quit the official Anglican church in Scotland and back a rival splinter movement in reaction to the vote supporting gay marriage in June last year.

A number of other churches have either left or are considering leaving in the wake of the decision to change the Scottish Episcopal Church's (SEC) definition of marriage as being between one man and one woman.

St Thomas' is one of the largest Anglican churches in the capital and the move to split from the SEC will be seen as a major blow to Scottish bishops trying to hold together the deeply opposed factions over same-sex marriage.

The Rev David McCarthy, Rector at St Thomas' told The Sunday Telegraph the decision had been a "very painful" one.

"We have not done it easily. We have had many tears and many sleepless nights. It is a tragic necessity," he said. "But it is the Scottish Episcopal Church who are leaving us. They are leaving orthodoxy."

The church's decision to permit gay marriage has put it at odds with the majority of Anglicans around the world. Last October sanctions were imposed on the SEC by leaders of the global Anglican Communion, restricting Scottish bishops from representing the group at interfaith meetings and from voting on decisions about policy or teaching.

The Most Reverend Mark Strange, Primus of the SEC, defiantly defended the decision although he admitted it was "one that has caused some hurt and anger in parts of the Anglican communion".

He said at the time: "I will do all I can to rebuild relationships, but that will be done from the position our church has now reached in accordance with its synodical processes and in the belief that love means love."

Even within the evangelical congregation at St Thomas' the decision was a controversial one and around a fifth have walked out since a vote confirmed the decision in May.

"I expected if we got to this stage we would lose people. But I suspect if we had gone the other way [and stayed in the SEC] we would have lost a lot more people," Mr McCarthy said.

"I would have walked," he added.

"If it was one person who left that would have been bad enough. It is not great. I am not happy about it. But we have not pushed anyone out. We have not said to anyone who disagreed 'you have got to leave'."

Mr McCarthy suggested that when the Church of England finally considers any potential changes to its teaching on marriage in 2020, "alternative oversight" will be offered for conservatives who oppose the changes.

"That was not offered here," he said. "The bishops are not willing to surrender any of their power.

"With new people come through for ordinations they will make a big thing about obedience. It is all very controlling from the bishops."

A spokesman for the SEC told The Sunday Telegraph that the numbers choosing to leave were small.

"We understand that the decision to allow gay marriage in church is difficult for some. It is always regrettable when people chose to leave.

"We have been working very hard to try and maintain unity."