A letter from the Anglican diocesan director of education raises the possibility of action against National Union of Teachers members who backed a motion critical of council plans to expand faith schools. The motion also demanded a review of faith schools' admission policies It was passed at an NUT meeting last month and won support from staff at both CofE and Roman Catholic schools.
The row could prove embarrassing for the Anglican Church as the Bishop of Blackburn, Alan Chesters, is chairman of the CofE's board of education.
In his letter to teachers, Canon Peter Ballard, diocesan director of education, said: "I hope you will take the opportunity of ensuring that this motion is not passed. If the motion is passed I am sure that guidance will need to be sought by all governors regarding its implication for those NUT members employed in church schools."
A teacher at a CofE school in Blackburn said: "I felt very threatened. It sounded like they were saying we had to go along with anything they said. I am not against faith schools but I have seen cases where church schools will admit anyone white rather than an Asian.
"If we had more balanced admissions policies then we wouldn't have the racial tensions that we have seen across many northern towns. We need a rational, open debate. For the Church to prevent that makes me upset."
The standard contract for CofE schools requires teachers to uphold the ethos of the school. But Brian Peacock, NUT secretary in Blackburn, said:
"Members in church schools are concerned that they could be penalised for following their consciences."
Canon Ballard denied the letter was a threat. He said no action would be taken against NUT members. But he said: "It would have been odd for me not to have done anything. If you sign a contract you should not undermine the ethos of the school where you work."
Keith Porteous Wood of the National Secular Society said: "This is a shocking piece of blackmail. It should be no business of the church to threaten people's careers because they are engaging in legal and democratic activity."