A Conservative MP has described proposals to allow gay marriage as "completely nuts".
In the House of Commons, Peter Bone urged the Church of England to block the plans, as it believed marriage had to be "between a man and a woman".
Fellow Conservative Tony Baldry, the second church estates commissioner, promised it would make "detailed submissions" to the government.
But the Home Office said all couples should have the choice of marriage.
A consultation is under way on proposals to allow same-sex couples to marry in civil ceremonies in the same way as opposite-sex couples can.
In the Commons, Mr Baldry said: "So far as the Church of England, the Roman Catholic Church and many other faith groups are concerned, marriage is a union between one man and one woman.
"That is the point we are putting forward responsibly and clearly in the consultation paper."
But speaking at Commons questions, Mr Bone, MP for Wellingborough in Northamptonshire, said: "Wouldn't it just be very simple to write back and say: 'Marriage is between a man and a woman so this is completely nuts'?"
A Home Office spokeswoman said: "If a couple love each other and want to commit to a life together, this government believes they should have the option of a civil marriage irrespective of their sexual orientation.
"We are working closely with all those who have an interest in the area to understand their views."
She added: "We are absolutely not changing religious marriage, or requiring religious groups to go against their traditions.
"Our consultation will look at how to open up civil marriage to same-sex couples."