The Bishop of Grantham, Rt Rev Nicholas Chamberlain, has received high-level support from the most senior official in the Anglican communion after controversy erupted over his sexuality.

Chamberlain has been backed by Dr Josiah Idowu-Fearon, the secretary general of the Anglican Communion, who said in a statement: "It is clear that Bishop Nicholas has abided by the guidelines set down by the Church. In fact, his lifestyle would make him acceptable to serve the church at any time in its history. I reject the suggestion that his appointment is an 'error'.

"I do recognise that this is a sensitive area for many people whatever their convictions. It is also a difficult time for Bishop Nicholas with revelations about his private life being made public in such a dramatic way, against his will, by anonymous sources that seem to be out to make trouble."

He added: "The Anglican Communion is a worldwide family and, like any family, we don't agree on everything. But we are committed to working together on difficult issues. I want to reassure the Communion of my commitment to what was set out at the Lambeth conference in 1998 – that human sexuality finds it full expression in marriage between a man and woman. But all baptised, faithful and believing people are loved by God and full members of the body of Christ regardless of their sexual orientation. The Anglican Communion has never made sexual orientation a condition of eligibility to hold office within the church and I reject the suggestion that it has."

Chamberlain was consecrated as suffragan Bishop of Grantham in November 2015 and everyone involved in the ceremony was aware of his sexuality. He became the first bishop to declare publicly that he is gay after being told by a Sunday newspaper that it would reveal his sexuality. He is in a long-term but celibate relationship.

The Archbishop of Canterbury said in a statement last week: "I am and have been fully aware of Bishop Nick's long-term, committed relationship. His appointment as bishop of Grantham was made on the basis of his skills and calling to serve the church in the diocese of Lincoln. He lives within the bishops' guidelines and his sexuality is completely irrelevant to his office."

In a letter to parishes in his Lincoln diocese, Chamberlain's senior bishop Rt Rev Christopher Lowson said: "I am satisfied now, as I was at the time of his appointment, that Bishop Nicholas fully understands, and lives by, the House of Bishops' guidance on issues in human sexuality. For me, and for those who assisted in his appointment, the fact that Bishop Nicholas is gay is not, and has never been, a determining factor."

However, Chamberlain was trenchantly attacked by the conservative GAFCON Anglican grouping, which declared his appointment a "major error". It said: "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.

"This news story will be seen by many orthodox Anglicans as yet more evidence that the clear biblical teaching in the Church of England on sin and salvation, human personhood, singleness, sex and marriage is being eroded and conformed to the values of secular society."