Nadine Labaki is a Lebanese actor and director whose latest film, Capernaum (meaning confusion or chaos in Arabic), won the jury prize at the 2018 Cannes film festival and has since been nominated for a Bafta (beaten by Roma) and an Academy Award. The film tells the story of a 12-year-old boy, Zain, who lives in a Beirut slum and whose parents are incapable of taking care of him. Having run away from home, he lives for a while with an illegal immigrant from Ethiopia, Rahil. None of those who appear in the film is a professional actor.

How did you come to start thinking about Capernaum?
In Lebanon, we are exposed to the sight of children suffering on a daily basis. They are there on the streets, selling gum or flowers or carrying heavy loads, such as gas tanks. Sometimes, they’re just lying there. I once saw this kid on a cement block in the middle of the road at one o’clock in the morning. He wanted to sleep, but he couldn’t. It began with feeling responsible, with wanting to become the voice of these kids. I thought: if I stay silent, I’m complicit in this crime – and it is a crime that we allow this to happen. I don’t know how we live with ourselves. These children are in perpetual danger. So I started going out with my co-writers to the most difficult neighbourhoods – to the slums, to the detention centres, to the courts – just watching.

The boy at the centre of the film, Zain, decides to sue his parents. Where did you get that idea?
I asked the children I spoke to if they were happy to be alive and for most the answer was no. One of them told me: “I don’t know why I was born if no one is going to love me, if no one is going to kiss me before I go to sleep, if I’m going to be beaten up every day.”

One day, it hit me. This is going to be the story of a child who says: no more. For the character of Zain’s mother, I was inspired by a woman who’d had 16 children, seven of whom died from neglect.

How did you find Zain Al Rafeea, the boy who plays Zain? His is a truly remarkable performance.
We did a street casting and one of my team found him. He was a Syrian refugee, an angry child, but very wise. He didn’t go to school. He was very small because of malnutrition. He’s in Norway now, with his family, and we’re making a documentary about that. What’s amazing is how many of the things in the film became true. When Rahil is arrested in the film, for instance: we shot that and two days later Yordanos Shiferaw, who plays her, was arrested in real life because, like her character, she, too, didn’t have any papers.

How have people in Lebanon responded to the film?
In two ways. Some are ashamed. They knew it was happening, but perhaps not the extent of it. They are shocked and it’s creating a huge discussion, a movement for change. Then there’s the other reaction, the people who say: no, this doesn’t exist. This isn’t our country. They don’t want to look in the mirror and see their flaws.

What is it like, making a film in Lebanon? How did you fund Capernaum, for instance?
You’re on your own. My husband [the musician and composer Khaled Mouzanar] produced it, as well as writing the score. He mortgaged our house without even telling me. We shot for six months. It’s not a case of arriving noisily, closing off streets with big vans and all that. You must become invisible.

Is it difficult as a female director in Beirut?
I’ve never felt that. It’s very difficult to make a film anyway in Lebanon: there’s no film industry. Perhaps that’s part of it. We’re doing it from scratch. We’re not entering a man’s world. It’s a clean page. In fact, there are more women than men working in film in Lebanon.

Where did your interest in film first come from?
My grandfather used to have a movie theatre in the village where my father was born. It was a small, humble cinema, like the one in Cinema Paradiso, but I remember very well my father describing to me the projection room, how he loved the smell of the reels. Thanks to that, he dreamed of a different life and though he was too poor to become a film-maker – he is an electronics engineer – perhaps that stayed with me. The other thing was the war in Lebanon. As children, me and my sister, who is also a film-maker, were confined. We lived behind sandbags. But we were lucky: we also lived above a small video store. We would wait for the power to come back on and then we would watch the same VHS tapes over and over again. It allowed us to escape our reality.

Do you worry for Lebanon again now?
Of course. Refugees [following the war in Syria] now make up half of the population. We feel like we’re on the verge of collapse. It’s chaos. It’s a capernaum, like my film. But that’s why I stay: I want to have a say.

Where were you when you heard Capernaum had been nominated for an Oscar?
I was at home with my crew. We went crazy. I had called Zain in Norway and I could see him in his classroom with his teacher and friends and they got the news on a laptop the same time as we did. Of course, he will be coming to the Oscars with us.

Will this turn your head? Is Lebanon likely to lose you to Los Angeles?
No, I’m very grounded. Of course I’ve received lots of scripts, but I want to make films that count. Making a film is so draining; when I finished Capernaum, I’d changed physically. You should do it only if you have something to say and the only reason I want to win is so I get those 30 seconds in which to speak. I want to make them matter. For me, film-making and activism are one and the same thing. I really do believe cinema can effect social change.

• Capernaum is released in the UK on 22 February