He said he was concerned about the implications for teenagers if the age of consent was lowered from 18 to 16.
He was speaking after the Bishop of Oxford, the Right Rev Richard Harries, issued a plea for the law on homosexual sex to be softened.
The Bishop of Southwell is a member of the Bishops' committee set up to review homosexuality, which is chaired by the Bishop of Oxford.
"There must be protection for those who are vulnerable and whose sexuality is not formed by the age of 16," he said.
"As a member of the group I am concerned that lowering the age of consent will endanger these people."
He pointed out that the proposals had moral, ethical and social implications.
"The Church of England expressed its views in General Synod in 1987, and the House of Bishops in their statement, Issues in Human Sexuality, in 1991," he said.
"Both are clear that heterosexual marriage is the proper setting ordained by God for sexual activity.
"I agree with this view, endorsed by the vast majority of Christians around the world and I believe that God expects this standard of all Christians whether they are clergy or lay people."
The Bishop said that although the decriminalising of consenting homosexual practice was a question of human rights and equality on which Parliament would make its own judgment, legislators had a responsibility to act not just for individual rights but for the future good of "our families, people and nation."
He said: "While the Church condemns all forms of homophobia which deny respect to any of our fellow human beings, whatever their orientation, it continues to uphold the received teaching on marriage and human sexuality."