The era of 'European Christendom' has passed and it is time for a new Reformation to wipe out the 'sinful' practices of gay sex and gay marriage, according to the leader of the Anglican church's largest evangelical province.

Archbishop and primate of Nigeria Nicholas Okoh, who heads the conservative Gafcon grouping in the Anglican Communion, has compared the crisis over gay marriage to the battle between the heretic Arius and St Athanasius that rocked the church of the fourth century.

That battle centred on the nature of the Trinity. Arius believed, against what came to be the wider orthodoxy, that 'there was a time when the son was not'.

And controversially, Okoh has offered to provide 'missionary bishops' to give oversight conservative Anglicans anywhere in the world who object to the liberal drift towards acceptance of gay marriage.

Okoh says in his June letter to GAFCON Anglicans: 'The doctrine of the Holy Trinity is vital. Without it, we cannot speak truly of God in a way that is faithful to the Bible. However, in the fourth century the Church was nearly overwhelmed by the Arians. They were the followers of Arius, who claimed that the Son was a created being, not really God.

'If the Church had continued to follow Arius, the Christian faith would have been lost. To deny the full divinity of Jesus strikes at the heart of the Christian message that God was in Christ reconciling the world to himself. St Athanasius is still remembered as the man who was willing to make a costly stand against this heresy.'

The Christian Church is facing a similar struggle for the integrity of the gospel in this era, he continues, and refers to the decision by the Scottish Episcopal Church to change its doctrine to allow gay marriage. This follows similar decisions by the Episcopal Church of the US and the Anglican Church of Canada.

Okoh says: 'This attempt to redefine marriage is not a secondary issue about which we can agree to disagree and continue to walk together. It means that Jesus was mistaken when he taught that marriage was between a man and a woman and that sex outside of such a marriage is a sin. It is a radical rejection of the authority of Scripture. The Church claims that it can consecrate behaviour that God's Word clearly teaches to be sinful. According to the Bible, this behaviour, without repentance, separates those who practice it from his kingdom.'

Okoh compares the consecration of Andy Lines as a 'missionary bishop' by GAFCON conservatives to the actions of Athanasius consecrating orthodox bishops in dioceses led by Arians.

'This is not a step we have taken lightly, but from the beginning GAFCON has been committed to standing with the marginalised.

'Requests for help from Scottish orthodox leaders to the Archbishop of Canterbury were turned down. Indeed, the Primus of the Scottish Episcopal Church told his General Synod last year that the Archbishop of Canterbury, had assured him that he would welcome the Scottish Church to the 2020 Lambeth Conference even if it chose to change its marriage canon to include same sex unions.

'So now GAFCON stands ready to recognise and support orthodox Anglicans in Scotland and elsewhere in Europe as the drift away from apostolic faith and order continues. For reasons of mission and conscience, we can expect to find a growing number of orthodox Anglican congregations needing oversight outside traditional structures, as is already the case with the Anglican Mission in England.

'The creation of a missionary bishop for Europe is an historic moment. It is a recognition that the era of European Christendom has passed and that in this 500th anniversary year of the Reformation, a new start is being made by building global partnerships for mission.

'So let us be strong. Let us stand with the marginalised and work tirelessly for the continuing reformation of our beloved Communion.'