A junior defence minister has distanced himself from David Cameron’s plan to legalise marriage for same-sex couples.

Gerald Howarth told The Telegraph that Tory MPs should not be forced to vote in support of changing the legal definition of marriage if the issue is put before Parliament.

Mr Cameron expressed support for homosexual marriage in his speech at the Tory conference this week.

“We’re consulting on legalising gay marriage. To anyone who has reservations, I say: Yes, it’s about equality, but it’s also about something else: commitment,” he said.

“Conservatives believe in the ties that bind us; that society is stronger when we make vows to each other and support each other.

“So I don’t support gay marriage despite being a Conservative. I support gay marriage because I am a Conservative.”

At present, homosexual couples are allowed to enter into civil partnerships which give them similar legal protection to married couples, but the term “marriage” is used to define heterosexual unions only.

Mr Howarth, MP for Aldershot, said that MPs should be given a free vote on the issue as it is a matter of “conscience”.

According to the newspaper, the MP believed many Christians would be “very concerned” by the proposal.

He said: “Some of my best friends are in civil partnerships, which is fine, but I think it would be a step too far to suggest that this is marriage.

“I take the view that marriage can only be between a man and a woman. That is what Christian marriage is about.”

Christian groups expressed grave concern about the Government’s plan to redefine marriage after Equality Minister Lynne Featherstone announced last month that a public consultation would be launched in March.

At the time of the announcement, various newspapers reported that the consultation was being launched after the personal intervention of Mr Cameron.

The Evangelical Alliance said that the Government should seek to protect marriage rather than redefine it.

It warned that the institution of marriage would be devalued if it were redefined to include same-sex unions.

The alliance said: “We support addressing injustices suffered by people who choose gay lifestyles, and would welcome many measures to secure reasonable and fair access to public goods and services.

“However, despite numerous assurances in 2005 (and many since) that civil partnerships would suffice in meeting demands for equality, it now seems that liberalism knows no limits.”