The Saturday interview: Pearl and Daisy Lowe

Last September a £35 vintage black polyester dress with a cream lace trim caused the kind of fuss in the fashion world usually reserved for Kate Moss's collections for Topshop. Designed by Pearl Lowe, once a minor Britpop star, the dress sold out in two hours. Peacocks, a budget retailer that managed to be around for over a century without generating much fuss, had to set up a waiting list for the first time in its history. Courtney Love tweeted a message to Lowe asking for a dress to be couriered to her New York hotel. Natalie Imbruglia and Sharleen Spiteri managed to get hold of one. And, after waiting for a few weeks, television presenter Holly Willoughby wore hers on This Morning.

Lowe's new collection for Peacocks – a black dress with lace bows, a simple floral dress, a polka-dot dress – was launched this week. Fashion writers blogged and tweeted about the vintage-style dresses for weeks in advance. The collections sell so well because they are easy to wear and hugely flattering, with sleeves and nipped-in waists; they come in sizes 8 to 18 and manage to look unique, like great flea-market finds.

The fact Lowe is so well connected helps, too. Before moving to a big house in Somerset with her family – she is married to Supergrass drummer Danny Goffey – she was part of the mid-90s Primrose Hill set that included Kate Moss, Sadie Frost, Sienna Miller, Jude Law and Rhys Ifans. It helps, too, that Lowe's daughter Daisy is a supermodel who has modelled her last two Peacocks collections. Daisy is equally well connected: her friend Alexa Chung bought the black polyester dress, and she is a regular on the catwalks of Vivienne Westwood and Chanel shows.

Daisy has been modelling since she was signed by Select at 15 and, at 22, is the height of cool. Pearl Lowe reinvented herself a decade ago, when she started designing lace curtains and cushions; since 2006 she has been making handmade dresses, first for Liberty's and then for small London boutiques. She has always been a gifted self-publicist, inviting endless magazines and newspapers into her country house and appearing on the front of Hello! with Daisy when she married Goffey in late 2008. The press, both tabloids and broadsheets, has in turn been infatuated with Pearl for more than a decade.

There has been a kind of car-crash fascination with Pearl's endless public discussion of her addiction to cocaine and heroin. Harriet Quick, fashion features director of Vogue, says that "the raw material of Pearl and Daisy's story is not great; it's not as though Pearl married Keith Richards." But, she adds, "in the last five years, fashion has opened up and it's become easier for people to think, 'I can do a line.' We are following on from America, where everyone wants to make a buck out of fashion. And the fact that Pearl also has a 'back from hell' story obviously touches people."

When I meet Pearl for lunch at Babington House, a private members' club near her Somerset home, she has been talking for less than 10 minutes before suddenly announcing: "I've been six years sober! Six years!" There's no one around to overhear such a declaration. Perhaps Pearl, 40, is not so much telling the world as herself: as a recovering addict, she needs to keep celebrating her sobriety. She certainly looks great, with those big, generous eyes, a long bob and a dog walker's lithe body. She sips orange juice and texts Daisy, who is in her room with her boyfriend, Matt Smith, taking a nap.

Pearl and Daisy are a unique mother-daughter act: Pearl is married to a rock star (albeit the drummer of a band that no longer exists), while Daisy is dating the incumbent Doctor Who, Matt Smith. Yet the reality of their relationship is not cool at all: as Daisy was growing up, Pearl was regularly taking drugs. It defines each of them to a degree; it makes you wonder if Daisy is angry.

And yet here she is, drifting through the restaurant in a pretty dress, tights, black boots and a battered, expensive-looking leather jacket. She kisses her mum, hugs her tight and steals her orange juice. When dressed up for fashion shoots, Daisy is often overtly sexual and provocative; today she is virtually free of makeup, and ridiculously beautiful.

They chat for a while as though alone. Pearl: "Did you hang out in the bar last night?" Daisy: "No, we had dinner and went to bed. We were supposed to watch the Banksy film and Black Swan and go for a night walk. But we just fell asleep. I woke up at 5.30am and all the lights were on, the curtains were open …" She gasps. "Ohmigod, we found two frogs in our room, one on top of the other. I think it was a baby frog and a mother frog. They were really cute but we had to pick them up and take them outside. Well, Matt had to."

She catches herself, glances at me: it's clear that Smith is out of bounds. Pearl, oblivious, keeps on chatting. "I'm so happy Daisy isn't like I used to be; I don't just mean not going to the bar last night, but her general lack of interest in big nights out." Daisy smiles. "I'm always calling mum and saying, 'I don't want to go to this party, do I have to go?' Don't get me wrong, I like to have a good party sometimes. But I really like having my friends over, cooking for them, dancing and then doing some painting. It's a really good night in … " It doesn't sound very rock'n'roll. "If you're talking about drugs, they don't agree with me; I'm too sensitive for them."

It seems that Daisy rebelled against her mum and Danny, whom Pearl met when Daisy was six, by deciding to be resolutely straight. Pearl has three children with Goffey – Alfie, 14; Frankie, 11, and Betty, 5 – and has been sober only since conceiving Betty. NME used to make nasty jokes about her giving birth to Alfie in the toilets of the Dublin Castle pub in Camden. For many years, taking drugs with a host of other north London celebrities was part of Pearl's life.

She insists, however, that her kids were oblivious to the drugs. "People used to be round at ours all night and then Danny would start ordering cabs while I opened the windows, lit the Diptyque candles and got the Hoover out. At 6am I'd finally go to bed and then get up and take the kids to school."

I ask Daisy what this was like for her. "I was aware there were lots of cool people in the house. I had no idea mum was doing drugs." Pearl continues: "When Daisy was 16 she asked me if I'd ever smoked spliff … " Daisy smiles and pokes at her green minestrone soup.

It has been suggested in other interviews that Pearl was often so out of it that Daisy had to look after Alfie and then Frankie, changing their nappies and feeding them. Daisy, laid back until now, sits up straight and almost shouts. "No, no, no. I've always talked about having a strong maternal instinct … when Mum was pregnant with Alfie, everyone kept saying that I was going to be really jealous of the baby. I took it upon myself to go against what everyone expected and look after him. I would always wake up early – as young kids do – and give him formula, watch Rugrats with him."

Pearl: "Bearing in mind I'd have done the night feeds with him." Daisy, shrugging: "I was just trying to be a nice daughter."

If this is well-rehearsed PR banter, it doesn't feel like it. Possibly because, as the conversation continues, it becomes clear that it has taken hard work for Pearl and Daisy to be so close. Pearl has always struggled with depression; when Frankie was five she sought help in a clinic. "It wasn't easy. Danny was away on tour with Supergrass so much, and looking after the kids was down to me. I was dreadfully unhappy."

Eventually, she began to realise that she had to leave London, the drugs, the social life, the madness. She found a house to rent in Hampshire and was all set to leave when Daisy, then 15, announced she wasn't coming. "It was the worst period of my entire life," says Pearl. "I can seriously say that I felt like ending it all. I didn't want to split my family up. I knew that if I stayed in London I wouldn't survive."

Daisy edges first towards her mother and then to the other end of the table, where she spears broccoli as she talks. "But I didn't understand that; I was only 15. I was a pain in the arse, but I didn't want you to go. I didn't want you to leave London. We had to keep talking and talking, but it was … " She drifts off. "Let's just say there's been a lot of healing since then." Daisy moved in with her maternal grandmother, got a Saturday job at Agent Provocateur and signed to Select Models.

To the outside world it looked as though Daisy's life was charmed. The reality was much more complicated. For years she had wanted to know who her biological dad was; Pearl had assumed it was Bronner Handwerger, a holistic doctor now based in San Diego with whom she had a short relationship. But Daisy worked out that, because of their respective blood groups, he couldn't be. Pearl puts her hand on Daisy's arm and says softly: "In a way I was too scared to find out. I kept thinking it was too late, but it's never too late." Pearl suspected it might be Gavin Rossdale, a British rock star now living in LA who was once her best friend. "I kept looking at Daisy's eyes and nose and thinking I couldn't live a lie any more."

So, when Daisy was 15, Rossdale took a paternity test and discovered he was her father. Pearl says Rossdale has refused to talk to her since finding out – "I lost a best friend, but found the truth" – while Daisy is in regular contact with him. She looks at her mum. "I hate the fact that you two don't get on. It would make life a lot easier and brighter if you did."

I ask Daisy if she too suffers from depression. "I've definitely got it in me. I'm better than I've ever been. I've given myself a hard time in the past: you've got a lovely family, a great boyfriend, great friends, a great job – it's so out of order for you to feel this way. As soon as I stood up and stared it in the face, I accepted it. It flies away a lot faster."

Out of the window I spot Smith striding up and down the lawn, learning his lines for the next series of Doctor Who. Daisy stares out of the window and smiles. "Aaaah, bless him!" We all three gaze at him for a moment. Daisy pulls herself away first. "Mum and Danny did everything they could for us, sending us to the best schools, making lovely family dinners, letting us have friends round, encouraging us to be open. Granted, my childhood wasn't conventional, but it was full of love.

"If ever I'm in trouble I ring my mum. She knows me better than anyone and has great life experience. There is no one else that can fix problems like she does."

In 2007, Pearl wrote a memoir of addiction, All That Glitters, about the years in London that almost killed her. She still grimaces when talking about those hazy years and how she wasn't "the best mother I could be". With anyone else, this might be maddening, but with Pearl the sentiment is so heartfelt it's hard to feel angry, although you do wonder if she will ever be at peace with herself.

A little later, I see Pearl, Daisy and Smith huddled together at one end of a bench in the garden. It's the first warm day of the year and there's no reason for them all to be sitting so close together, and they have no idea I can see them. Whatever Pearl may have done wrong, she also did something right.