The leading group of conservative Anglicans worldwide has criticised the appointment of the gay Bishop of Grantham as a "major error".

Bishop Nicholas Chamberlain revealed he was gay yesterday after a Sunday newspaper threatened to out him.

He told BBC News he had never sought to make it a secret. "My focus and priority has been on my ministry, on serving God, on serving God's people. And I do that, as I always have done, as a gay man."

He added: "My sexuality is part of who I am rather than the whole of who I am".

The Global Fellowship of Confessing Anglicans, or Gafcon, said in a statement: "We note with prayerful concern the revelation that Nicholas Chamberlain, Bishop of Grantham, is in a same sex relationship."

Gafcon conceded that even though he is in a committed relationship, Chamberlain lives within the guidelines of the bishops of the Church of England which stipulates that gay clergy must be celibate. Nor has he campaigned publicly for a change in the church's teaching on sex and marriage.

"We do not doubt that he has many gifts as a leader and pastor," said Gafcon. "However there are aspects of this appointment which are a serious cause for concern for biblically orthodox Anglicans around the world, and therefore we believe that this appointment is a major error."

The group, which represents conservative evangelical Anglicans worldwide but particularly in the global south countries of Asia and Africa, warned that the news will "exacerbate" the divisions caused by the attempt in 2003 to make Canon Jeffrey John the Bishop of Reading. Dr John is currently Dean of St Albans.

"We remain opposed to the guidelines for clergy and Bishops, permitting them to be in same sex relationships as long as they publicly declare that the relationship is not sexual. This creates confusion in terms of the church's teaching on the nature of sex and marriage, and it is not modelling a helpful way to live, given the reality of our humanity, and temptation to sexual sin," said Gafcon in the statement, signed by Archbishop Peter Jensen, general secretary and Canon Andy Lines, chairman of Gafcon UK.

Tracy Byrne, of the Lesbian and Gay Christian Movement, said: "It should be noted that Bishop Nick is not in a civil partnership, and so it is perhaps unwise to draw a direct parallel with a married opposite-sex couple. However, his relationship is clearly an important and significant one, in which he has flourished and within the context of which he has been supported in his ministry as a fine priest and pastor, and now bishop.

"Those who made the appointment were aware of Bishop Nick's relationship and were satisfied that he is living within the discipline of the church. Whilst that space for accomodating priests in celibate gay relatinships is an unsatisfactory one for many of us, and a costly one for those who have made that choice, it is nevertheless a valid choice to make, both for the individual concerned, and for those making the appointment. It is a choice which should be respected, and those relationships and individuals should be honoured."