This weekend will see some of the first gay marriage ceremonies in the UK, signalling the belief in many people's mind that the gay marriage debate is over and that those in favour have won out.

But American Professor Robert Lopez, founder of the International Children's Rights Institute, believes that a new debate is now just beginning, over the rights and wrongs of gay and lesbian couples adopting children to raise as their own.

Christian Concern quoted him as saying: "There is no 'right to a child' or 'right to be a parent' or 'right to adopt', but a child has a natural born right to a mum and dad."

He has a particular investment in this issue, having been raised by two women in a lesbian relationship, and he has come to the UK to make his case.

Christian Today spoke to him about his beliefs and why he holds them.

CT: Why do you feel the need to go as far as to call it a "right" to have a mother and a father figure?

RL: It is a fundamental right because every child is born with a mother and a father. If we reject the concept of natural born rights that are self-evident, then we have no rights at all.

That is the most natural born and self-evident right of all because that is what makes us all equal as human beings, that we come from a mother and a father.

CT: What would you say to the view that those brought up by two mothers or two fathers might be differently brought up, but not necessarily worse off than those without parents of both genders?

RL: I would say they've lost something. Regardless of the economic conditions or social conditions that might be appropriate for them to develop well over the course of their childhood, they have lost a part of their identity and a connection to their heritage, and that's very serious.

CT: What are the specific advantages of having both a mother and a father?

RL: The problem is that it's very hard to come up with specifics because the word 'advantage' and the word 'disadvantage' have been so often used in very vague terms in social science research.

Often research will look into questions of whether children are well adjusted emotionally, or whether they suffer from any kind of emotional afflictions in childhood, but these questions don't speak to the deeper questions of a person's identity.

We know from speaking to adoptees and listening to their testimonies – adoptees in general I should say, not just children adopted by same-sex couples – that there is a need to connect with where you came from.

I know that I felt that very deeply in my late twenties, even though I grew up with the love of two women who I still love and cherish to this day, the fact was I needed dad. That was half of who I was.

It's a human longing that's hard to put in economic terms or in statistical terms, but it is something very real and I believe that it is almost universal.

CT: Could you describe that 'longing' you talked about? How would you characterise that?

RL: I do think there are things that are ineffable, that are almost indescribable and very difficult to put into language. As I grew older, I just sensed that there was a hole in my life. I felt there was a relationship that was important that had been stripped from me. I felt a sense of loss, anger, and a powerful longing to re-connect and rebuild that.

It's a longing like anything else, the kind of longings that govern our relationships. You might have a yearning for a romantic relationship, or a yearning for a friendship. It's the same kind of thing, you feel something inside you that really compels you to want to rebuild this connection to somebody else.

CT: What about the question of character traits and developmental issues? What are the particular traits or issues that emerge as a result of only having parents of one gender?

RL: It did in my case, but I don't want to speak too generally about this. There is a great deal of social science research that seems to give us conflicting evidence.

I have dealt with a lot of other children of same sex couples and I've listened to their testimonials and I would say that a majority of them thought there was confusion about their sexual identity, and confusion about their gender identity. But there were some who didn't, so its hard to talk about a general rule.

In my case, I was effeminate growing up. I did try to fill the gap of the missing father figure by being very promiscuous in my teen years in terms of having lots of sexual encounters with older men.

It took a long time for me to get away from that behaviour because it was self-destructive. I was confused about whether I was gay or straight.

CT: Why is do you think that other male or female role models such as uncles or aunts, or friends of the family and the like, can't fill the role left by not having a parent of a particular gender?

RL: Because they're not really committed to you in the way that a father is. Those are incidental relationships, they come and they go, and it just doesn't feel permanent.

My mother tried very hard to bring male role models in, and I know a lot of lesbian couples do that when they have sons. But those are people who don't really have a stable connection to you. Maybe you can model behaviour after them, but they're not really invested in you because they're not part of your home.

CT: Is your ultimate position then that lesbian and gay couples just should not adopt?

RL: Absolutely. I think they should put the needs of children first, and they need to envision a life for themselves where they can show love to children by being good aunts and uncles.

Maybe also by being a foster care home, I believe they make good foster couples. But they should not adopt, and they should not use third party reproduction systems because those are permanent lifelong deprivations of the child of a mum or a dad, and there's no way for the child to reverse it. That's why I don't support homosexual adoption, but I support foster care.

CT: You talk about the right to a mother and father being born out of a natural fact, the fact that we all have a mother and a father biologically. If technologies were to adapt, and gay and lesbian couples were able to conceive a child without third party means, would that change your view?

RL: No, it would not. I'm coming from an American perspective where in the Declaration of Independence, it is written that "all men are created equal and they are endowed with inalienable rights". I read that in a secular sense that all of us are created equal in that we all have a mother and a father.

If we move towards a society where some people have two mothers and some people have a mother and a father, that throws into doubt the entire system of natural rights that our system is based on. I suspect that English law is based on similar precepts even if they're not stated the same way.

I think we have to think of having a mother and a father similarly to the way we think of free speech, or habeas corpus. They're things that we don't prove that we have by trying to measure outcomes. We just have them because we're born and we're human.

If we undermine this, if we undermine this basis of our identity in having a mother and a father, I think we undermine everything about human rights. It's really very fundamental and elementary.

CT: You've talked about this in terms of gay and lesbian couples, do you think also that the state has a role in assisting in the nurturing of children in single parent families as well?

RL: Here's the thing, I am not approaching the children's rights issue as an anti-gay issue. I think we need to cultivate a society where men do not abandon their children. When you're talking about a single mother, they have a right to the support and specifically the financial support, definitely.

You can't just impregnate someone and then disappear. The child has a right to that other person. That person has to provide for that child that they've conceived. I do think the state has to be involved in making sure people fulfil those obligations. That means the state has to use some of its legislative force as well.

CT: What about scenerios where for one reason or another, one of the parents dies. Should the state be more involved in those circumstances, in providing assistance?

RL: What's different when one of the parents dies is that the child can at least remember and honour the memory of that person. They knew who the person was. I think the child's right to a mum and dad is still fulfilled if their connection to that memory is honoured.

I do think the state should be deeply involved in providing for widows and widowers. Going all the way back to antiquity, every single culture has measured social justice by how people provide for widows and orphans. It's in the Bible, it's in ancient Greek and Roman texts. That's definitely important. Communities and states have to get involved and have to help.

CT: You talked briefly about the Bible there. While there are many people who believe that the Bible specifically speaks out against homosexual behaviour, do you think there are passages that also support your position more specifically? The idea that motherhood and fatherhood are intrinsic?

RL: From a Biblical perspective, you've got to remember that 'honour thy father and mother' is one of the ten commandments.

However my overall belief isn't linked to the Bible. I think the state has to recognise gay relationships, that's why I support civil unions in the US, and why I think that it's good that we saw civil partnerships in the UK. One of the things that broke my heart when my mother died was that there was no legal recognition of her relationship with her lesbian partner. That was really bad.

Where I draw the line is where you want to honour the relationship of two gay people at the expense of honouring a child's relationship to a mother and father.

CT: You spoke earlier on about conflicting social scientific studies on this issue. Are there any particular studies that have stood out to you?

RL: There are hundreds of them. I'm most well versed in the two most recent ones, the Mark Regnerus study and the Douglas Allen study. I liked the fact that they were randomised and they used metrics that were very clear like whether or not they graduated from university, or whether they ever went on public assistance.

The bulk of the earlier studies used very vague measurements. Things like 'are they well adjusted', 'do they love their parents', 'do they feel safe'. These are very low thresholds to measure whether someone has had a disadvantage or not. But I'm sceptical about all of them because I don't think you can attach a statistical value to having a mum and a dad.

CT: What do you hope these protests you're organising in the UK will accomplish? What is your aim in coming here?

RL: I'm hoping that the discourse will shift now that the gay marriage debate is over, and that we can look at not just parenting, but all of the different reforms we make in terms of adoption and divorce.

We also need to look very carefully at third party reproduction. I would like to ban sperm banking and female surrogacy. I really want us to have a proper ethical discussion about the really worrying implications present in all these new family structures.

I think that the most important thing is to close the door on the gay marriage debate, but to also make it clear that a new door has opened, and there's a lot more to talk about.