"I don't like him."

This father of two teen girls — aged 14 and 19 — is in a bind: his elder daughter is dating a boy he doesn't like.

Not because he supports the wrong football team. Or because he doesn't really fit in. It's because of the way he talks to his daughter.

"She's lost all her confidence. He seems to decide things for her. And I'm worried, down the track, he'll treat her worse — like you read about."

What should he do?

A father's relationship with his teen daughter can be tricky, but it can be downright complex when a boyfriend enters the home.

What's Dad's relationship with boyfriend? What rules need to be employed? And is it possible to influence how daughter sees her new relationship?

Many fathers underestimate the power they have in determining their daughter's romantic happiness. Repeatedly, research has shown that dads can determine the type of person their daughters date, their focus on education, when they start to have sex, and what they will accept in a relationship.

"What is surprising," according to father-daughter expert and author Linda Nielsen, "is not that fathers have such an impact on their daughters' relationships with men, but that they generally have more impact than mothers do."

Yet, on this topic, often fathers are not sure where to start.

"How do I handle boyfriends?" one father asked me, while I was researching Fathers and Daughters.

"How do dads become a person who can talk about boys without seeming like we are preaching, being totally unrealistic or chauvinistic?" another said.

Girls are just as at sea. "Can you cover boyfriends, please? Dad would be a bit agitated about that. Can you tell him to chill?"

Or, "Can you do something on stereotypes? I reckon it would be strange asking Dad, not my mum, about boys. It would be weird."

Teenage girls developing relationships with boys can be confronting for fathers. ( ABC Riverland: Catherine Heuzenroeder )

What not to do

So before we get to the "dos", let's address a couple of "don'ts" for dads.

Firstly, don't lie. "My dad won't tell me when he had his first girlfriend or anything like that. He just lies about all that. He says he had his first girlfriend when he was 30," Chloe says.

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And don't follow the lead of this girl's dad. "When your daughter says 'OMG, I'm so fat', DON'T reply, as my dad does, by saying 'Yes you are looking a little big', but say something along the lines of 'No, you're not, you're perfect as you are'," Tamara, 17 says.

Don't put yourself in competition for your daughter's attention, either. "My dad was very surprisingly accepting of a boy. He just got upset that I stopped spending time with him!"

And don't befriend a daughter's new boyfriend. This happens more than you might imagine.

In my research, fathers routinely invite their daughter's boyfriend to the football on a Friday night. Or fishing with a group of blokes on the weekend.

Psychologist and author Andrew Fuller says he knows some fathers who have secretly stayed friends with their daughter's boyfriend once the couple had parted.

"So many men, because they don't invest in their own friendship world, are vulnerable to this," he says.

It's a chance to let your daughter open up

If teen girls won't broach the subject of boys, that doesn't mean fathers can't.

"I told Mum first," Eliza says. "But once I did talk to Dad he was quite supportive … that made me open up more about other stuff to him."

Mothers tend to be more encouraging. "My mum's actually very supportive of relationships," Emma says. "She's like, 'Emma, go get yourself a boyfriend. Have some fun while you are still young'. I've started to get some friends who are boys and Dad just laughs at me. Dad doesn't have a lot of interest but Mum's pushing me."

Sophia is the same. "My mum would be happy for me but my dad would definitely be intimidating to the boy. He's told me a hundred times I can't have a boyfriend until I'm 30." And that is still 14 years away.

Fathers worry about their daughters' wellbeing once boys enter the arena. ( Flickr: verkeorg )

Be the model for how you want your daughter treated

Girls learn from the behaviour their fathers model. That means fathers can show daughters, through their own treatment of women, including the girl's mother, the respect that should colour a relationship.

School principal Linda Douglas says girls learn from the specific interactions they see — how their father engages with their mother, the relationship between their father and sister, and their father and themselves.

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Angela White from Adolescent Success says the father's influence is so strong because he constitutes the girl's first male relationship.

"For most 13-year-old girls, that might be the only model they will have had. So fathers are teaching their daughters how to relate to men without realising."

Negative relationships can be role-modelled. One principal says Mum and Dad "openly squabbling" has an impact on girls, especially in Year 10. That's because it's the age when they're more aware of how relationships operate and understand the role gender plays.

"Some of those kids really crave attention, and the risk is they'll crave it from someone else, without thinking carefully about it," he says. "That's what scares me."

Listen before lecturing

Adelaide psychologist Kirrilie Smout says fathers will have a perspective on relationships that mothers might not have and need to ask questions of their daughters.

Indeed, she says, they should ask 10 questions before offering any piece of advice, including: "Tell me what you think of this guy?"; "How do you manage that?"; and "Why do you think he does that?"

"If you have that conversation and then say 'You know what I think?', you get to shape how girls think about their relationships with boys. That's a gift," Ms Smout says.

* Names of girls quoted in this article have been changed.

Madonna King is the author of Fathers and Daughters (Hachette).