A US woman raised by a lesbian couple after her birth parents separated has spoken out against same sex marriage.

In a comment piece published by right-wing US website The Federalist Heather Barwick writes that despite supporting gay marriage, she has come out against it “not because you’re gay” but “because of the nature of the same-sex relationship.”

Stressing her own positive experiences of being raised by two women in a loving and committed relationship, Mrs Barwick, who concedes “wasn’t a great guy”, who failed to “come around” after the collapse of his relationship with her mother.

She writes that her father’s “absence created a huge hole in me, and I ached every day for a dad.”

She continues: “I loved my mom’s partner, but another mom could never have replaced the father I lost. “

Mrs Barwick, a 31-year-old committed Christian wife and mother of four, who campaigned alongside her mother and her mother’s friends for LGBT rights, claims her attitudes changed when she became a mother.

“And it’s only now, as I watch my children loving and being loved by their father each day, that I can see the beauty and wisdom in traditional marriage and parenting.”

“Same-sex marriage and parenting withholds either a mother or father from a child while telling him or her that it doesn’t matter,” she writes.

Mrs Barwick's piece comes amid changing attitudes – and increased discussion – around same-sex marriage in the US.

Same-sex marriage is recognised by the federal government and couples can be legally married in 36 US states, the District of Columbia and 22 Native American tribal jurisdictions.

But her comment piece has not been well-received.

Abigail Garner, who was raised by two fathers and advocates for children with LGBT parents, said she failed to understand Mrs Barwick’s reasoning.