Orthodox and evangelical Anglicans are questioning the Church of England's decision to allow clergy in civil partnerships to be bishops.
The House of Bishops announced yesterday that clergy in civil partnerships would be accepted into the episcopate on condition that they remain celibate.
Anglican Mainstream warned that it would "not be credible" for a person in a civil partnership to give assurances of celibacy.
"Most people assume that civil partnerships are sexual relationships. It is casuistical to claim that they are not," he said.
"This is presumably why many clergy in such partnerships refuse to 'give assurances' to their bishops that theirs is a 'non-sexual' relationship.
"Since a decision to move from the current position would be a grave departure from the Church's doctrine and discipline it should be made by Bishops in Synod not by bishops alone."
It also said that a bishop known to be in civil partnership "could hardly be a focus of unity nor be a bishop for the whole church".
"Such an appointment would be a very divisive move both within the Church of England and in the wider Anglican Communion," the group said.
The Church of England Evangelical Council said the move would "spread confusion" and "be taken as an effort to conform to the spirit of the age".
It added that the Church has a "poor record" on enforcing celibacy.
"By its timing, the bishops appear stung by the national reaction of outrage to the rejection by General Synod of legislation to legalise the consecration of women as bishops," the group said.
"If by this statement they are trying to mend fences with the general populace, showing they are truly in touch with the mind of the nation, they are profoundly out of touch with the reality of civil partnerships, most of which are seen as a focus for sexual activity, not simply an arrangement for tax purposes."