Dr Justin Coulson previews the 'honest conversations' set to appear on Parental Guidance

Parenting expert Dr Justin Coulson had his work cut out for him when he put his hand up to co-host what many call the Hunger Games of parenting, Parental Guidance.

The show is a battle of the fittest parenting style, where each week different styles of raising children are put to the ultimate test through a series of challenges that can break even the strongest and most patient of parents.

Meanwhile, the mums and dads not competing in the challenges are tasked with watching how the others perform, commenting on their parenting and ultimately, voting, for the most effective style.

Luckily, being a dad of six, Justin is more than used to a little finger-pointing and name-calling. Although, he says he doesn't need to call on his stern voice too often.

READ MORE: Meet the families of Parental Guidance

"There were one or two very, very tense moments," Justin, who co-hosts with Today's Ally Langdon, told 9Entertainment. "But we asked for everyone to be upfront and honest about what they were seeing and feeling because it's only through honest conversations that we get to have the insight and awareness that we may otherwise lack."

One of the instances Justin is referring to is the conversation the group have around smacking in the first episode. Strict parents Andrew and Miriam reveal to the group that they use this as a form of discipline on their three children. It's not received well by the other parents.

"You're violating someone else's body," says French parent Donna.

"It's abuse," comments Nature parent Liadhan.

READ MORE: A guide to the different parenting styles on Parental Guidance

Justin himself takes a very strong stance on this topic.

"I categorically reject any suggestion that there's any redemptive aspects to smacking children," he says firmly. "The research is clear, there's no evidence and there's no moral or philosophical reason that we should be supporting a physical, punitive approach when it comes to disciplining our kids, or hurting our kids, rather."

But Strict parents Andrew and Miriam are not there to be defensive and Justin praises the way they handle the criticism from the other parents and grow from the experience on the show.

"Andrew acknowledged how much he and Miriam now have to talk about in relation to the way they raise their kids," Justin said. "I thought it was beautiful, he accepted what he heard and went away and thought about it."

And they're not the only parents who used the opportunity to reflect on their parenting and make some positive changes.

"The openness and vulnerability of the parents overall was really special, and we get to see with pretty much all of the parents at various stages," Justin revealed, clearly proud of how far they had come. "I'm delighted about how all the parents grew and the way they came together and celebrated great parenting."

Justin adds that he thinks parents at home will take a lot away from the show too.

"I think it's impossible to watch this show without thinking what you do as a parent and wondering how you can do it better, and the great thing is the show gives you plenty of ideas as to how you can do it better."

Parental Guidance airs Monday to Wednesday at 7.30pm on Nine and 9Now. Catch up on every episode on 9Now.