They said the Canadians should be ejected with the liberal American Episcopal Church, which backed the consecration of Anglicanism's first openly-gay bishop last year.

Their intervention has badly damaged efforts by Dr Williams and other Anglican leaders to broker peace between the factions on homosexuality.

Last week it appeared that the Canadian synod had avoided a clash with the conservatives when it decided to delay a vote on homosexual blessings at its meeting in St Catharines, Ontario.

The postponement was even praised by Dr Williams, who said in a statement that it would help the work of the Lambeth Commission, the body he set up to try to maintain unity.

But a late amendment introduced by liberals at the synod infuriated the Global South group of conservative primates, who represent more than 50 million Anglicans in the 70 million-strong worldwide Church.

Liberals said the amendment, which was designed to placate homosexuals angry about the delay over blessings, was not intended to have theological significance.

Conservative primates, including a member of Dr Williams's Lambeth Commission, said using the term "sanctity" put same-sex unions on a par with marriage and pre-empted debate on their doctrinal status.

In a statement on behalf of 22 Global South primates, Archbishop Gregory Venables, the Primate of the Southern Cone (South America), said: "The use of the word sanctify means that the whole issue has already been decided and that is devastating.

"It's saying that God has agreed to bless same-sex unions as the word carries the implication that this isn't just right, but that this is God's will and he has set it apart for the human race.

"It's rewriting the Christian faith. There's nothing in the Bible about the sanctity of same-sex relationships. Canada's action merely confirms the sad reality of the fragmentation of the Anglican family.

"We would like to see them expelled. This is going against Christian teaching and they should either repent or shut the door behind themselves."

Archbishop Drexel Gomez, the Primate of the West Indies and a member of the Commission, added: "It is completely unacceptable to Bible believing orthodox Christians that same-sex unions are described as 'holy'. Such language is reserved for marriage alone.

"The attempt to give 'committed adult same-sex relationships' the same theological stature as marriage exacerbates the crisis in the Communion and will reap devastating consequences."

Traditionalists said that, in Church language, sanctity meant blessed, holy or sacred. It appears twice in the Anglican Book of Common Prayer regarding marriage ceremonies.

Their reaction will destabilise the Lambeth Commission's efforts to resolve differences between conservatives and liberals in their final report to be published in October.

Senior churchmen are starting to concede that the worldwide Church could acrimoniously fall apart and two rival churches could be created.

If so, Dr Williams would be torn between liberals and conservatives and the Church of England's general synod might have to decide to which group he should be aligned.

END