Samantha Morton: Why does our boldest film actress feel so persecuted for her loyalty to British indie cinema?

Outside the Bestwood Village Social Club, tucked into a former mining community on the outskirts of Nottingham, it's the high summer of 2006. Caravans creak in the heat in the car park. Sweating blokes jangling tool belts scurry from truck to truck. Camera equipment and cabling lie in piles in the bright sunshine.

But inside the small, squat social this hot July afternoon, it's like we've entered some pre-punk Tardis: we suddenly find ourselves at the Hard Rock in Manchester, it's the winter of 1972/1973, and the atmosphere is smoky and grey. Even the kids milling around the bar dressed in glam-rock finery – elaborate cockatoo haircuts, lightning-shaped make-up slashed over faces, awash with leopard-print – appear monochrome somehow. But the anticipation is electric: this is the night David Bowie, toting his just-released album Ziggy Stardust And The Spiders From Mars, comes to town.

A lad fetches over pints to a lass, crisps clutched in his mouth. " Cheese and onion, my favourite," says the girl, who will become Deborah Curtis. "Mine too," grins Ian Curtis. "I'm really looking excited for this," the girl continues in a flat Macclesfield accent. "I weren't really into Bowie before."

He tells her that her ex-boyfriend has OK'd him asking her out. "Bit presumptuous," says a mock-affronted Deborah, smiling excitedly as she sips her pint.

So began Ian and Deborah Curtis's first date. Eighteen months later, in August 1975, the teenagers would be married. Four years after that, Ian's band, Joy Division, released their debut album. One year after that, on the eve of an American tour and just prior to the release of their landmark single "Love Will Tear us Apart", Ian Curtis hung himself. He was 23.

In Bestwood it's day 15 of the 42-day shoot of Control: Anton Corbijn's film about the short but complex life of Ian Curtis, based on Deborah Curtis's memoir Touching From A Distance. Newcomer Sam Riley, in a performance that has already wowed Cannes, plays Ian. Samantha Morton, in a performance that underlines her claim to be Britain's most versatile, most complete, most challenging and most quietly brilliant actress, plays Deborah.

"I'm not a fan in general of films about peoples lives," says Morton in her caravan dressing-room between takes. She's in character, dressed in early 1970s frumpery, complete with Wendy-Craig-in-Butterflies wig, but eases her aching feet by slipping off her platform sandals. "I don't get the point in a lot of biopics," she continues, "they're boring. You know what's gonna happen. You're just watching actors show off."

But Control, she says, was different. Morton has long been a huge fan of Joy Division. She religiously listens to music while making films, to help get herself in the mindset of characters – the band's "She's Lost Control" blasting repeatedly through her headphones, helped her prepare for the role of recently bereaved and off-the-rails Iris in her breakthrough film, Under The Skin (1997). She's a big admirer of Corbijn's work as a rock photographer. And she loved Deborah's book, an honest, unflinching, moving biography by the woman Ian married before he was famous, and whom he betrayed – much to his torment – by having an affair with a Belgian journalist.

"But I had this really weird thing where I wanted to do the film but I thought, 'is the part gonna be interesting enough for me as an actor, to spend eight weeks playing?' I like to stretch my acting muscles. I just love films, and I don't wanna disrespect myself.

"Equally, when I had the opportunity to speak to Anton about playing the role, I got really possessive about it. I was protective of Deborah and Ian and [their daughter] Natalie, and really bizarrely protective of how she was portrayed. I didn't want anyone else to be in there. If I hadn't got the part I would have been really traumatised."

Thirteen months later, in the bar of The Hospital multi-media centre in London's Covent Garden, Morton still looks traumatised. She's just emerged from a screening of Control. It's the first time she's seen it. When asked what she thinks of it, she is initially – literally – at a loss for words.

"My personal reaction to it is that I'm just so moved," she says after an inordinate pause. "I think it's utterly original in its take on a biopic. I could have watched another two hours."

She talks – rambles – for some time about the film, and art, and artists' responsibilities to the source material and the real people behind the story. "Obviously I've only just seen it so I'm not giving you soundbites, I'm thinking this through as I'm talking to you."

But, yes, much as she dislikes seeing herself on screen ("I just watched what Sam was doing. Oh, he's incredible") she was completely transported by Corbijn's film. The 30-year-old actress is pale and (initially at least) quiet this afternoon and not, I think because she's heavily pregnant with her second child. Samantha Morton looks – in a profound way – shellshocked by the cinematic experience she's just had.

This is what she's like: intense, sober, smart, wary, often scorchingly honest. Brave, too. A glutton for punishing roles. When I met Morton in Nottingham last summer she'd just finished shooting back-to-back films: Channel 4 drama Longford, in which she played Myra Hindley; Shekhar Kapur's Elizabeth follow-up The Golden Age, in which she plays Mary, Queen Of Scots; wayward American auteur Harmony Korine's Mister Lonely, in which she plays a Marilyn Monroe impersonator. When I met her last month she had just completed filming Synecdoche, the directorial debut of famously out-there scriptwriter Charlie Kaufman (Being John Malkovich, Adaptation).

Over the course of the elaborate, intricate movie about a New York theatre director (he rebuilds Manhattan inside a studio), her character ages from 30 to 64. Next year, after she has her baby, she'll take the role of Bernadette Devlin, the Northern Ireland peace campaigner. How's that for a run of full-on performances?

Morton is, if you like, the anti-Keira Knightley. She has less in common with peers such as Kate Winslet and Rachel Weisz than she does with James McAvoy. Like the fast-rising star of Atonement she is focused on her job, and on improving her skills, often brow-furrowingly earnestly so, and is studious in her avoidance of the limelight – even if she used to be cast as one of the happenin' north London set hanging about with Kate'*'Sadie'*'Rhys.

"You're photographed out with Kate Moss 'cause you know Kate Moss and you're automatically part of that world," she snorts. "I've never lived in Primrose Hill!"

When she lets herself go, Morton is great fun – the last time I interviewed her we got very drunk in an Islington restaurant and she divulged lots of delicious off-the-record morsels – and her laugh is a brilliantly unrestrained snorting cackle. However, these days she's more likely to put in a public appearance in support of one of the children's charities to which she devotes a serious amount of her time and emotions.

She thinks "you lose the essence of your life" if you don't remain socially engaged. "It's fantastic to strive towards a nice life where you eat nice organic food and your children go to a nice school and you can afford nice clothes and nice perfume and the hypoallergenic make-up. But there's never a day goes by, and I mean this from the bottom of my heart, that I don't think about where I'm from."

Morton grew up in Nottingham. She had an infamously chaotic, splintered childhood: parents' marriage breaks down, dad sets up home with Morton's teenage neighbour and babysitter, Morton shuttles from foster parent to foster parent to care home; adolescent Morton runs a little wild. In Control, Nottingham stands in for Macclesfield – the latter is a more modern-looking these days – but Nottingham remains, in places, authentically 1970s.

How was it going back to her hometown to film Control?

"Oh gosh," she sighs. "Having had a really odd childhood, filming on the streets where I slept rough and was homeless was really weird. I left like, like Dick Whittington! Aged 16, came to the bright lights of London to work at the Royal Court Theatre, and here I am. I mean, I do go back to Nottingham to visit family but it's really hard."

Did she go back with her head held high? Was it a case of, I transcended my difficult upbringing and am returning having made something of myself...

"But I had always made something of myself," she interjects. " I understand the phrase you just used – but I was never any less than I am today. And I've always been my spirit, when I was four and when I was in homeless hostels. Your spirit is your spirit, whether you're religious or whatever." But, yes, she concedes, filming on those streets, her streets, was hard. "It made me realise how forgotten a lot of these towns are."

Morton is fed up talking about this stuff. As she points out, more than half her life has been free of the teenage waywardness that so titillates the tabloids to this day. She's sued – and won – five times after newspapers printed falsehoods about her, complete fallacies such as the time she lay drunk on the floor of a Dublin hotel or took ecstasy with Ken Livingstone. (Let's say it again: neither incident happened.) What about, she wonders rhetorically, the two Oscar nominations she's received, for Woody Allen's Sweet And Lowdown and Jim Sheridan's In America? Or about her brilliant performance in the title role in Morvern Callar, or her achievement in Steven Spielberg's Minority Report, opposite Tom Cruise? Why not write about those instead?

"I've been an ambassador for this country, and also for independent cinema," she says. It sounds less like bumptiousness and more like pent-up agitation (Morton, stung too many times, doesn't do many interviews any more). And anyway, she's right. "I keep earning very little money but OK [amounts] for me because at least I'm earning, and doing independent film after independent film," she says, all but thumping the table You don't see me fucking off to Hollywood. I haven't done that, and there's a reason for that. I actively choose not to be in X-Men 3. I actively choose not to be the wife in of these big movies."

Presumably she was offered movies such as that after Minority Report?

"Yeah, and I still am. But I just think we haven't really got a film industry and if we all fuck off over there..." She stops. "Excuse me, it makes me so upset. So the Daily Mail, they constantly write 'troubled person' and such nasty things. But yet Kate Winslet, who was Oscar-nominated nine times or something and is an incredible talent, and all these other wonderful actors that we have, but yet they don't... it's like she's constantly supported. She once got into a bit of trouble over a magazine cover she did [GQ dramatically airbrushed a cover image of Winslet]. But other than that, they just constantly talk about her acting."

Personal background aside, Morton, it seems, is too "edgy" in her career choices for such unconditional media testimonials. She wouldn't, surely, have it any other way. 'After her performance in Sweet And Lowdown, Morton was offered a part in director Curtis Hanson's Wonder Boys. He was hot off the Oscar-winning triumph of LA Confidential. She turned down the part of a coquettish student with a crush on middle-aged academic and writer Michael Douglas; Katie Holmes, the future Mrs Cruise, took the part instead. A difficult decision?

"No," she says blankly, as if to say "don't be so stupid" . "I went and did [American indie film] Jesus Son [instead]. That script was what I responded to – the part, the script, the writer, the whole package. Every single part, whether its Dreaming Of Jospeh Lees or Enduring Love, whatever it is, I have to personally go, "Oh, I see, I get that." I leave it to the agents and managers and lawyers to give me reasoning and say, "OK, a business move would be to do this..."

She smiles. "But I'm lucky, I'm surrounded by people that want me to be happy as an actor. I'm really lucky actually – I get to do really good parts and be satisfied. You might be at a party and you meet an actor, and they've come off something – 'that was a pile of shit. But it made $200m at the box office!' And you're like, 'Yeah, but you've had a grim six months and it was a pile of shit! Would you go and see that?' And they wanna do the parts that I do. And I go, 'but you've got three houses..."'

Sam Morton has only the one house, albeit in the beautiful, time-capsule street in London's East End that is also home to Tracey Emin and Gilbert & George. She shares it with Esme, seven, her daughter by actor Charlie Creed-Miles, and her fiancé Harry Holm, a pop video director and the son of Ian Holm. Is it true that Johnny Borrell of Razorlight is going to be Holm's best man?

"Yeah."

How do they know each other?

"That's their business!" she says, flashing a smile of steel. She has no time for celebrity tittle-tattle. Work and family aside, her focus is on the charitable causes she holds dear.

"And that's often a hindrance, because sometimes it's hard to be able to relax... I have too much respect for people. My contemporaries aren't just other actors – they're the friend that I lived with when I was younger, who's got three kids and can't afford to go to work – she gets more dole money than she does [working]. Then my other mate who does go to bloody work and is in a cramped one-bed council flat with two kids and her husband and can't afford to get out of that – yet she works. It's just all... I dunno."

Morton sighs, empathetic pain writ large across her face. And don't get her started on the state of the NHS (her stepfather has cancer yet was misdiagnosed for a year). Or children's care provision (her sister works with kids). Or the Government's treatment of the Army – her brother, formerly a Marine serving in Afghanistan, is now a private security guard at the British Embassy in Baghdad; some of the stories he tells her about shoddy equipment... Most of all, her work as an ambassador for Save The Children keeps her awake

"I will check the internet for at least an hour every morning scanning worldwide news to do with child abuse. So if you're constantly putting yourself in an environment where you're checking up on social economics or homelessness problems, if you keep yourself aware of it, you don't really have a day off. So when I say it's sometimes a hindrance, it's because some people are able to go on holiday and not think about someone being abused right now, someone being hurt right now. It's kind of in me."

Samantha Morton smiles a wan smile. Her roles, for all their intensity, don't kill her – "Did playing Myra Hindley infect me? God no, I'm not a method actor!" – but this stuff does. Having experienced the rough side of life, she wouldn't have it any other way. As with everything to do with this mercurial, compelling agit-actor, Morton dives in with heart and head.

'Control' opens on 5 October

Grand Sam: Ms Morton's five must-sees

Under The Skin (1997)

Morton loses her mother and her way, drinking to excess and giving herself to a variety of men. A tremendously visceral performance

Sweet and Lowdown (1999)

Playing a deaf-mute in Woody Allen's period film about a jazz guitarist in 1930s America, Morton won an Oscar nomination for her silent, sparkling performance

Morvern Callar (2002)

Morton makes the Highland lass heroine of Alan Warner's novel all her own in Lynne Ramsay's poetic, occasionally bleak adaptation

Minority Report (2002)

With her head shaved, Morton was eerily captivating as the imperilled " pre-cog" who can see the future and thereby help cop-on-the-run Tom Cruise

Code 46 (2003)

Michael Winterbottom's love story casts Morton as forger of ID papers in future-Shanghai. Detective Tim Robbins can't help but fall for her