The Evangelical Group of the General Synod has amended its basis of faith to include a new clause affirming marriage as a union "between one man and one woman".
EGGS members voted overwhelmingly in support of the clause, which has been added to section 4 of the group's basis of faith - the section dealing with its beliefs on sin.
The vote took place at a fringe meeting of the Church of England General Synod during its York session earlier this week.
The newly inserted clause 4.1.2. asserts: "We acknowledge God's creation of humankind as male and female and the unchangeable standard of Christian marriage between one man and one woman as the proper place for sexual intimacy and the basis of the family.
"We repent of our failures to maintain this standard and call for a renewed commitment to lifelong fidelity in marriage and abstinence for those who are not married."
Another new clause added to the basis of faith affirms Jesus Christ as the only Saviour of mankind from sin, judgement and hell for all who come to him through repentance and faith.
Rev John Dunnett, Chair of the Evangelical Group on General Synod (EGGS) said the new clauses reflected the views of a majority of evangelicals within the Church of England.
"I am pleased to report that the Evangelical Group on General Synod overwhelmingly supported a motion to bring our basis of faith into line with that of the Church of England Evangelical Council (CEEC)," he said.
"The CEEC represents and speaks for the majority of evangelicals in the Church of England, and by supporting the proposed changes EGGS has demonstrated that it wishes to be part of this family."