The Anglican Primate of Nigeria, Archbishop Peter Akinola, has warned that he may lead a boycott of the Lambeth Conference 2008, following news that two controversial bishops did not receive invitations from the Archbishop of Canterbury, the Anglican Communion's spiritual leader.

Dr Akinola revealed he was greatly upset that Archbishop Dr Rowan Williams did not issue an invitation to Bishop Martyn Minns, missionary bishop of the Convocation of Anglicans in North America (CANA), an orthodox Anglican splinter group and offshoot of the Church of Nigeria. He now oversees some 34 orthodox Anglican congregations in CANA that are dissident from the US Episcopal Church.

The first set of invitations for Lambeth 2008 - the Anglican Communion's global decennial gathering - were sent out by Archbishop Williams to more than 850 bishops last week.

The Rt Rev Martyn Minns said: "While the immediate attention is focused on the invitation list, it should be remembered that this crisis in the Anglican Communion is not about a few individual bishops but about a worldwide Communion that is torn at its deepest level."

Openly gay Bishop V Gene Robinson of New Hampshire was also not invited to Lambeth 2008.

While reports indicate the non-invitation of the two bishops is likely to provoke debate, Dr Williams stated he has to reserve the right to withhold invitations from "bishops whose appointment, actions or manner of life have caused exceptionally serious division or scandal within the Communion."

He also recalled that invitations are issued on a personal basis by the Archbishop of Canterbury and in the invitation letter stated that the conference has "no 'constitution' or formal powers".

The invitations went out four months before the US Episcopal Church is scheduled to respond to the requests of the Primates (Anglican leaders) to make an unequivocal pledge not to authorise same-sex blessings and confirm another openly gay bishop.

Archbishop Akinola has been one of the most outspoken critics of the acceptance of homosexuality in the Anglican Communion.

He recently ordained Bishop Minns as a "missionary bishop" to serve the spiritual needs of like-minded Anglicans in America.

Dr Akinola has said the failure to invite Bishop Minns could be "viewed as withholding invitation to the entire House of Bishops of the Church of Nigeria".

He warned that he might now refuse to attend the Lambeth Conference, and encourage all other Nigerian prelates to join him in boycotting the meetings.