The principal of Australia's only mainstream Catholic school signed up to the Safe Schools Coalition says he is under "considerable pressure" to withdraw from the anti-bullying program.

St Joseph's College principal Paul Tobias said he had received emails from conservative Catholics – who are not part of the school community – who claimed it was wrong for a Catholic entity to be involved in the program.

"This debate has put people like me in a particularly difficult position," he said.

"But I don't believe there is anything in the Catholic faith that should stop us from promoting inclusiveness, diversity, and tolerance."