A woman with lesbian mothers has has spoken about how how growing up without a father affected her childhood and why she believes same-sex marriage isn't good for children.

Millie Fontana, 24, detailed her life as a 'donor conceived child' to hundreds of people at the Australian Christian Lobby in 2015, in a speech which has started circulating on social media as debate heats up ahead of the postal vote on same-sex marriage.

In her recorded 13-minute speech, Ms Fontana claimed her testimony was 'unheard of because nobody wants to hear about the other side of the rainbow.'

'The side that is not catered for, that don't grow up happy and grow up with a dissenting idea of what a family structure should be.'

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Millie Fontana (pictured), who grew up with lesbian parents and came out against same-sex marriage, has detailed to the Australian Christian Lobby how growing up without a father affected her

Fontana, who campaigned in support of the plebiscite on same-sex marriage, said that 'Rainbow families' must be held accountable for how they create their families

Ms Fontana said that from a young age she felt that she 'wanted a father,' even though she couldn't 'even articulate what a father was.'

'I knew that I loved both of my parents but I could not place my finger on what it is I was missing inside myself.'

'When I hit school I started to realise through observing other children and their loving bonds with their fathers that I really was missing out on something special.'

'I was lied to throughout school, I was told that I didn't have a father or that perhaps they didn't know who he was.'

The 24-year-old said not having her father in her life made it 'very difficult for [her] to affirm a stable identity.'

'When they chose what parts of my identity were acceptable to reveal to me, they took something from me and where other children were able to look in the mirror and reconcile those missing parts and say I love my mothers or my fathers, I could not because in my eyes who were my parents to decide what parts of me were acceptable to reveal to me.'

Fontana, who campaigned in support of the plebiscite on same-sex marriage, said 'Rainbow families' must be held accountable for how they create their families.

'This is my main issue with the gay community right now,' she said earlier this year during an episode of the ABC series You Can't Ask That.

Millie Fontana, a woman with two lesbian mothers, is once again speaking out about how growing up without a father negatively affected her childhood

Millie's father was a friend of one of her mother's from high school, and they naturally conceived her and two brothers.

'He was open to a relationship with us if that's something that rose up in the future,' she said. 'But it was strongly insinuated that we were fatherless.'

Millie met her father when she was 11 years old, saying in previous interviews it was the first time she felt 'stable' in her adolescence.

'When I was a young kid, I didn't really want to bring people into my world,' she said on You Can't Ask That.

Millie, who said she wished she grew up with her father, believes same-sex unions should only be allowed if children are guaranteed access to their biological parents

'Having that understanding of who my father was would have benefited me to go into things like school...more confidently.'

Millie said she 'clung' to men in other families as she searched for a father figure of her own.

'I would spend an almost unhealthy amount of time at their houses because I was fascinated by the heterosexual family structure,' she said.

'I couldn't replace my actual father,' she added. 'It was still obvious to me there was quite a lot missing.'

Other children interviewed on the program said they never felt they missed out on anything because their parents didn't fit into traditional gender roles.

'It's not the fifties anymore, even in a heterosexual couple,' one interviewee remarked.

But Millie found herself yearning for a parent who would do 'dad things with their kids', which she referred to as 'sports things' and 'the whole barbeque thing'.

'I think a lot of parents in the same-sex community, one of them will try to masculinize themselves a little bit to make up for the lack of a father role,' she claimed.

Millie met her father when she was 11 years old, saying in previous interviews it was the first time she felt 'stable' in her adolescence

When Millie finally met her father, she found he had an 'air of graceful masculinity about him'.

'I know who I was,' she said. 'I knew who everyone was. I knew my heritage.'

Millie has said in the past that there are 'serious consequences' for children who are 'denied access to their biological parents'.

She also condemned anonymous donors.

Millie has said in the past that there are 'serious consequences' for children who are 'denied access to their biological parents'

'Anyone who wants to get an anonymous donor... just don't do it,' she said.

'Why would you do that when you could get a friend...where you've got the option of having an even bigger and better family instead of having one that's lacking something.'

Millie, who said she wished she grew up with her father, believes same-sex unions should only be allowed if children are guaranteed access to their biological parents.

'We [children of same-sex ­couples] want our mothers and ­fathers,' she said in October.

'I don't understand why ­society is so fiercely rejecting such a natural concept that is acceptable in every other family structure.'