MPs, peers and religious leaders have launched a petition in an attempt to block government plans to "redefine" marriage to allow gay couples to tie the knot.
Tory backbencher Fiona Bruce said she had lent her name to the 'Coalition for Marriage' petition because she wanted to protect children.
"Primarily I am supporting it as a mother, as well as an MP, because research shows over different cultures and different ages that children flourish when they are brought up in a secure family environment, and this traditionally has been marriage," she said.
The Congleton MP told The Huffington Post UK that her "first priority" was to maintain an institution which she said gave children "security and stability".
Bruce indicated she thought it would be intolerant of the government to bring in gay marriage and that ministers should instead support "distinct and different relationships".
"I think in a tolerant society there is a room to support support a variety of types of relationship, marriage is one."
She added: "Similarly we have civil partnerships."
Bruce's name is joined on the list by fellow Tories Edward Leigh, David Nuttall and Stewart Jackson. Labour MPs Jim Dobbin and Joe Benton have also signed up.
The petition is fronted by the former Archbishop of Cantebury, Lord Carey of Clifton, who told the Daily Mail that the plans were "one of the greatest political power grabs in history".
In September, it was announced that the coalition government would legislate for same-sex marriages by 2015, a proposal that Carey repeatedly described as "baffling".
David Cameron has urged his party to back the proposals, arguing that Conservatives should support the idea commitment.
"Conservatives believe in the ties that bind us; that society is stronger when we make vows to each other and support each other," he told the Tory party conference last year.
“So I don’t support gay marriage in spite of being a Conservative. I support gay marriage because I am a Conservative."
The prime minister has also been lent the perhaps unlikely support of Tim Montgomerie, the influential editor of the grassroots Tory website, Conservative Home.
Montgomerie argued that Conservatives should back gay marriage as giving equal rights to gay men and women would help to preserve the institution.
"Marriage is probably the most important Conservative institution and excluding people from it is therefore excluding people from Conservativism to a significant extent," he said.