Stacey Dooley is so fresh-faced she could pass for a teenager. But, at 32, she has been making investigative programmes for 12 years, and has clocked up 80-odd documentaries around the world, taking on terrorists, paedophile networks, rightwing extremists and international drug dealers. She has just returned from Syria, where she met European Islamic State brides for her first Panorama; and Nigeria, where she got to know Boko Haram’s female suicide bombers. Last year, she wrote a bestselling book about inspirational women and won Strictly Come Dancing. On Friday it was announced that she had signed a £250,000-a-year golden handcuffs deal to work only for the BBC.

Earlier this year, she found herself splashed across the tabloids – first for starting a relationship with her Strictly dance partner Kevin Clifton, then for being labelled “a white saviour” by the Labour MP David Lammy after making a Comic Relief documentary and posting a photo of herself and a young Ugandan child on social media. It’s been a busy old time.

Dooley is a one-off: a working-class woman who left school with no qualifications, swears like a trooper, reports from the world’s most hostile territories and frequently tops the TV ratings charts. She has achieved the seemingly impossible – presenting programmes about subjects so bleak they would make most BBC editors blanch, while encouraging a generation of news-shy young people to embrace world affairs. Women, children, the marginalised and the exploited are at the heart of her documentaries. Last year, she won an MBE for her services to journalism.

“Hi, I’m Stacey,” she says with a wink and a handshake when we meet in a London restaurant. Her fans might expect a hug – she is famously tactile in her documentaries – but perhaps the real Dooley is more complex than the empathetic naif who loves to tell it straight. Sure, she is warm and direct, but she is also businesslike.

Dooley says she is the hardest-working person she knows. “It’s one of my few talents,” she admits. “I’ve always had a decent work ethic, probably because of my mother, when it was just her and me. She just worked so hard. She’d get up at silly o’clock, clean her pal’s house, then do her day job, then work in pubs at night.” Dooley’s father, who had a drink problem, was not part of her life. Her mother later met her partner, Norman, and they had a child together – Dooley’s sister. Both girls were bridesmaids at their wedding. But it was the early years that shaped Dooley.

She grew up with her mother in Luton, in Bedfordshire, surrounded by rightwing extremists and Islamist fundamentalists. Stephen Yaxley-Lennon, AKA Tommy Robinson, went to her school (she confronted him and al-Muhajiroun activists in the film My Hometown Fanatics). Young Stacey was mouthy and opinionated. Again, she says, it was down to her mother. “My mum stands up for what she thinks is right. She’s tough.” Has Dooley got that toughness? “Yes. I’ve always been quite bloody-minded. You’ve got to have the courage to say what you believe.”

Stacey Dooley flanked by two officers in Face To Face With Bounty Hunters, her forthcoming BBC Three documentary. Photograph: Rachel Lob-Levyt/BBC/TI Media

That bloody-mindedness came into its own in her early teens. “I was a nightmare.” In what way? “I wasn’t frightened of authority. I just did whatever I wanted.” She started drinking, clubbing, bunking off school. “I probably drove my mum loopy. I wouldn’t come home and I’d be out smoking and drinking.” Anything else? “I’d steal.” She smiles. “Nothing ridiculous like cars. I’d just go down the Arndale and rob a couple of Morgan tops. The thing I nicked the most was blue eyeliner from the chemist. I was always wearing blue eyeliner and blue mascara, which, on reflection, probably wasn’t my best look.” Did she steal with friends? “Yes. But I was good. I never got caught.”

These days, she says, she’s a goody-goody – no smoking, no drinking, no tea-leafing. As for drugs, she has never touched them. She says she saw too much when she was growing up. “We lost a friend to drugs; we lost another friend to drink. He didn’t reach 18. We all used to drink. Then you get yourself in a mess and you fall asleep and choke on your own sick …” She trails off. “That wasn’t the moment I thought: ‘I’m never drinking again.’ But I’m sure it makes you think twice.”

Dooley says the story that she left school at 15 without qualifications is not quite right. She turned up for three of her GCSEs (English, Music and Biology), but she never bothered collecting her results. Her face lights up. “Maybe I did really well. I might have got three As and I’ve been underselling myself all this time!”

She sold perfume by day at Luton airport and did pub work in the evening, spending all her money on clothes – most of them cheap and throwaway. One day, her mother spotted an advert for young people who were obsessed with fast fashion to go to India and discover how their clothes were made. “It said: ‘Do you like travel, do you like fashion, do you like telly?’ And for me it was tick, tick, tick.” As soon as she applied for the job, she knew she would get it. Again, the Dooley confidence. “You’ve got to think: ‘Why not me?’ They’ve got to have someone.”

Watch Blood, Sweat and T-shirts now, 10 years on, and you can see that Dooley arrived almost fully formed. She was unfiltered, pasionate and addressed the camera as if it was her best friend. In one scene, after talking to a tiny boy who was sent by his family to work in a Bombay factory, she turns to the camera, outraged and tearful. “Sorry, the boss of the factory Mohammed was working at used to beat him up really bad, so he ran away. He’s just a baby and he got beaten up by a grown man. It just makes you feel sick.” The tears became another Dooley trademark.

After returning from India she was invited by the then controller of BBC Three, Danny Cohen, to make her own documentaries. She asked simple, heartfelt questions that trained journalists were often too polite or cerebral to ask. Occasionally, Dooley has almost become a self-parody – asking for a couple of minutes while she turns away to weep, ranting at the world’s injustices, wrapping her arms around a victim she has just met. But so much of her portfolio is amazing – asking an Isis fighter who said he had killed 900 people and raped 200 women: “What was going through your mind when these girls were screaming for you to stop and you don’t?”; telling a drug dealer he is a hypocrite because he wouldn’t dream of selling to his children; confronting women who have sold their children for sex.

Has she become addicted to violence and war zones like so many foreign correspondents? No, she says, she can’t wait to get away. So many people who do her work have PTSD, she says, but she’s lucky. She doesn’t even have nightmares. “I think it’s because my mind is clear … You have to look after yourself mentally when you’re making films about incest and paedophilia and cartels cutting people’s heads off.” After a tough day, she switches off by listening to Little Mix. (“I love Woman Like Me.” Does her work scare her? “I’m such a wimp. I don’t even like flying, so it is slightly ridiculous that I do this job.” She says she was most terrified in north-east Nigeria. “I was in Maiduguri, the birthplace of Boko Haram, and there were times when I thought I might have to leave early because I can’t handle feeling frightened like this. Every night you could hear the military shelling, and you’re thinking: ‘How am I going to get out?’” Did she tell her mother she was in Maiduguri? She grins. “No, I told her I was in Lagos.” How does your mum feel about you lying? “It’s for her own good because all she would do is panic.”

With Yazidi women soldiers at their training camp in Stacey on the Frontline: Girls, Guns and Isis. Photograph: Almudena Garcia-Parrado/BBC/Insight TWI/Almudena Garcia-Parrado

Dooley’s work has politicised her. After all the abuses she has witnessed in criminalised drugs and sex industries, she would consider legalising both. She has always voted Labour. “I always think it’s odd when people say: ‘I don’t give a fuck about politics,’ because it determines how you live.” We meet the day Boris Johnson moves into No 10. “I don’t know how long he’ll last,” she says.

Dooley knows she is not universally liked, and takes pride in it. “I’m not vanilla,” she says. “At the start of my career, some people were like: ‘This is a breath of fresh air’; others: ‘There are thousands of trained journalists that deserve her job.’” Is there an advantage to not being trained? She nods. “Middle-class journalists might not be able to connect with a girl who lives in Queens [in New York] and has been abused by her father in the same way that I can.” Anyway, she says, these days it’s harder to cling to her working-class roots. “It’s all balsamic vinegar and oat milk – I’ve got a middle-class palate now, whether I like it or not.”

Colleagues are less snobbish to her than they used to be, she says. What’s the worst thing they have said? “Oh God, I’ve had it all. Sometimes they would say: ‘Ooh, you’ve got holes in your jeans,’ or mimic my accent.” Did she give them a mouthful? “No.” Why not? “Because I don’t give a fuck what they think. Some people don’t understand why I’m there. But I work really hard and I deserve to be there. And our documentaries speak for themselves. We are always top three on iPlayer and often we are most watched factual. The only one we can’t beat is EastEnders.”

If some colleagues don’t appreciate the role she plays at the BBC, she certainly does. “We all pay our TV licence. It doesn’t matter whether you live on an estate in Luton or you live around the corner from Hyde Park and studied at Oxbridge – we all need to be heard. We all need to look at people on television and say: ‘Yeah, they represent me in some way.’ That’s where we’ve gone wrong in the past. I think the BBC would be the first to say current affairs is still too white and too middle-class and too male-heavy.”

Celebrating winning Strictly Come Dancing in December 2018 with Kevin Clifton. Photograph: Guy Levy/PA

What she says about people being heard is interesting, particularly in light of Lammy’s “white saviour” attack on her. She fought back ferociously on Twitter. Does she think she might have misjudged it – that it would have been better to say ‘Let’s have a chat’ rather than beat him into submission? “I did say that a couple of times, but they never pick up on it. I would love to have spoken to David.” Does she now think he had a point? “I would take on board the criticism and bear in mind that people have certain views and I can’t tell people how to feel. I would be mindful of that.” Would she do Comic Relief again? “I believe in what they do. As one of the richest countries in the world, we have a responsibility to help those in need. Going forward, I hope we’re able to keep raising money in a way that everyone feels comfy with.” It’s funny – for a moment she sounds like a politician.

When Dooley was invited to compete on Strictly, she was already well known. Now she is a household name. How has it changed her life? “There’s more interest in my personal life.” Is she surprised? “Yes.” Really? “Yes! What I’m surprised at is that I go to places like Syria and meet some of the most recognisable terrorists in the world or talk about things that will shape the global landscape – enormous topics that warrant front pages of papers – but they never go with that. They’ll always go with who I fancy or who I’m snogging.”

Rant over, she acknowledges that Strictly has been wonderful for her, despite the fact that her ex-partner, Sam Tucknott, now has custody of their bulldog Bernie. Was there a fight over Bernie? “No. It would be irresponsible of me to take Bernie because I’m never here. Sam is amazing with him, and if I wanted to see Bernie, he would let me.”

Dooley finds time to relax: ‘I said no to a lot of things I didn’t believe in. So I went back to the day job.’ Photograph: Sarah Lee/The Guardian

Her critics claim she has given up on the serious stuff for celebrity. Does it upset her? “Yeah, I think that’s an unfair statement. When you win Strictly, you can go down two paths. All the offers come in, and you can do very little work and put your name to things for lots of money, or you can go back to making documentaries in Syria and Nigeria and work really bloody hard. I said no to a lot of things I didn’t believe in. It’s not that I’m holier than thou, it’s just that it wasn’t for me. So I went back to the day job.”

I ask again if she really expected us not to be interested in her private life after Strictly. Well, maybe not, she says, but she could always hope. “Kev and I have agreed not to go into too much detail about our private lives because you can’t really indulge that and then ask for privacy. That’s why we’ve turned down interviews that have offered us tens of thousands of pounds. What I am happy to say is Kev’s amazing, I’m happy, life happens, I’ve got an amazing career and I’m very lucky.”

Did she expect to win Strictly? “I thought: ‘Why not – someone’s got to win it.’” Did she deserve to? “Yes!” she says instantly. “I worked really hard. I didn’t know how to waltz beforehand, I didn’t know what a ballroom frame looked like.” Did she work harder than everyone else? “Yes,” she says even more emphatically. She bursts out laughing. So the old Dooley work ethic triumphed? “Yes! My one skill.”

• Stacey Dooley: Face to Face with the Bounty Hunters is on BBC Three on Wednesday 31 July. Panorama: Stacey Meets the IS Brides is on BBC One on Monday 5 August