LONDON (Reuters) ? Almost half the world?s Anglican archbishops have mutinied over the divisive issue of gay clergy, demanding action from Archbishop of Canterbury Rowan Williams over ?unrepentant sexual immorality? in the church.

Their views, set out in a sharply worded open letter to Williams in which they attack his leadership, could put the 450-year-old church on the road to schism.

Two years of deepening divisions among the world?s 77 million Anglicans were sparked by the ordination of gay American bishop Gene Robinson and the blessing of same-sex marriages in Canada.

Williams has always been personally tolerant of gay clergy and at a meeting this week of the church?s governing synod in London, he called for reconciliation, a plea that clearly fell on deaf ears among Anglican leaders in the developing world.

Seventeen of the church?s 38 archbishops, headed by Nigeria?s Peter Akinola, said in the letter: ?We urge you to rethink your view and embrace the church?s consensus.

?We wonder whether your personal dissent from this consensus prevents you from taking the necessary steps to confront those churches that have embraced teaching contrary to the overwhelming testimony of the Anglican communion.?

The Church of England also provoked fury among traditionalists by allowing gay priests to register under Britain?s new civil partnership law, as long as they remain celibate.

African church leaders in particular fear that if Anglicanism takes a lenient line on homosexuality, its followers will turn to more conservative Christian churches or Islam.

In contrast to the regimented hierarchy of the much bigger Roman Catholic Church, the Anglican communion is a broad grouping of churches across 164 countries, run by consensus.

At the synod, Williams called for reconciliation through prayer, telling fellow clerics: ?We have to beware of poisoning the wells by doing our business with suspicion and hostility or lack of mutual respect.?

On Thursday, the open revolt against Williams? leadership provoked a crisply worded reply from his Lambeth Palace office.

?The Archbishop has made it clear since before his enthronement that neither he nor anyone else has any mandate to change the church?s teaching,? his spokesman said.

?If this letter is a contribution to the debate, then it is welcome, however robust. But if it is an attempt to foreclose the debate, it would seem to serve very little purpose indeed.?