The right of the Roman Catholic Church to veto teacher appointments in denominational schools is discriminatory and should be legally challenged, delegates overwhelmingly agreed.
In a surprising show of force, delegates instructed union officials to seek a Queen's Counsel ruling. Ian Close, Renfrewshire, said the Church's actions may contravene the European Convention on Human Rights, which UK law incorporates later this year.
Mr Close said the move would outlaw discrimination on religious grounds and may bring into question the 1918 Education Act in Scotland which laid down the Church's existing rights.
"This is not a challenge to Catholic education, far less a challenge to the Catholic Church. I want no support from people who are anti-Catholic. It is an issue about discrimination against some of our members and we frankly cannot avoid taking a view. It is an issue the EIS has dodged for decades," he said.
Mr Close said it was traditional in Catholic schools to restrict posts in senior management, biology, religious education and guidance but some councils had extended that to other departments. Some non-Catholics were being banned from applying for posts in subjects such as geography or maths.
Carole Cameron, Edinburgh, defending the Church's rights, said its mission was to defend the ethos of the Catholic school.
But Ian McCrone, Renfrewshire, said a colleague had applied to be a principal teacher of science but was told the post was only open to Church-approved candidates. Supply teachers were also having problems since more posts were being restricted.