Look back in anger: Samantha Morton makes her directorial debut

The feature-length drama The Unloved, the centrepiece of Channel's 4's Britain's Forgotten Children season about youngsters in care, has already been described as "Ken Loach on downers".

You could compare it to Loach's seminal polemic Cathy Come Home, or even liken it – with its rapt poetic attention to a provincial British city (in this case Nottingham) – to the work of Bill Douglas or Terence Davies. It's certainly among the more remarkable British TV dramas of the past 25 years.

But what is most astonishing about this bleak and beautiful film is that it marks the directorial debut of Samantha Morton – the actress who played Myra Hindley in Longford, Ian Curtis's wife in the Joy Division biopic Control and whose acting was described by her Minority Report co-star Tom Cruise as "lightning in a bottle". Morton's direction – a sort of raw European art-house aesthetic – may not be entirely original, but it is completely unexpected. Not that she intends shooting anything else.

"I made this because I had something to say," she says. "It's a bit like the manifesto of the Free Cinema movement, that films can't be anything but personal, and this is what I had to say. Maybe in another 20 years I might have something else to say."

Lindsay Anderson's Free Cinema movement of the 1950s, Wim Wenders's My American Friend ("my favourite film") and the Finnish director Aki Kaurismaki ("my hero") were Morton's role models as she stepped behind the camera for the first time. But the pictures Morton has been carrying around in her head for almost a lifetime are all hers. The Unloved is the semi-autobiographical story of the actress's upbringing at the hands of Nottinghamshire social services – "from a baby to an 18-year-old" – her parents having divorced when she was two.

She was 16, she says, and living in a hostel for the homeless when she first started storyboarding The Unloved – the title taken from a newspaper article she had read about young Nottingham prostitutes, one of them a girl Morton had known in care. "I was attending the Television Workshop in Nottingham and I said I wanted to make a play about my situation and where I lived. So we devised a play and we performed it for a couple of nights."

Now, 16 years later, The Unloved has been reborn as a Channel 4 drama with Robert Carlyle and Susan Lynch as the parents of the Morton character, 11-year-old Lucy. The drama follows Lucy's obliquely explained removal from the family home, and bewildering entry into a riotous care home overseen by some (at best) inadequate adults. She befriends her 16-year-old roommate, who is being sexually abused by a member of staff, and who takes Lucy shoplifting.

Lucy is played by a young actress Morton discovered at a drama workshop in Nottingham, Molly Windsor, who utters only a handful of lines during the whole film. Mostly it's just us watching her watching the awful things happening around her. It's a mesmerising performance.

How did Morton herself feel while shooting these scenes? "It was horrible to watch at times," she says. "To be honest, sometimes I know why I have made the film and other days I don't. I have worked very hard on being aware of my childhood but moving forward and not letting it bring me down emotionally. That is a hard thing – especially when you have children of your own and you remember what happened to you at that age.

"I have to be clear about this – it's not my autobiography. But how close is it? Well, it's exactly how it felt." She doesn't want to go into the specifics of her own abuse, but as Morton speaks about Lucy, glimpses of autobiography seem to emerge from the semi-autobiography. For example, I ask about a scene in which the children, under the tutelage of the sexually abusive care worker, are watching Jean Vigo's L'Atalante on television.

"It's to do with children, innocence and puppets," she says. "It sounds pretentious but when I was small I was around adults who were very educated and very manipulative with it. I felt I was being given a gift at times – whether it was music, film, literature or art – but actually they'd abuse those gifts to get at me. I have to be clear – there are similarities between me and Lucy, but my mum and dad and my eight brothers and sisters can all watch the film and go, 'We know that's not our story, but we get why she's done it'. As I've already said publicly, I love and respect my parents and I'm not about to exploit them."

If anything, the abuse suffered by Morton was worse that that experienced by Lucy in the film. Morton's mother moved in with an alcoholic, and her father used to beat her. She was made a ward of court aged eight. And Morton has revealed in a recent interview that she was once charged with attempted murder when she threatened to stab a girl who had been bullying her over a long period of time. Morton was convicted of a lesser charge and sentenced to 18 weeks at an attendance centre. Why did she hold back for The Unloved when she could have made it more harrowing?

"I wanted to make a film children would watch. This is the sort of film I'd loved to have seen when I was 13. I wanted kids who normally watch EastEnders to find it on television and see something that feels a little different. I used to watch TV programmes about being in care and think about the characters I knew and none of the TV depictions felt very real to me. The closest was films like Kes and Ladybird, Ladybird that showed the aspect of loneliness, of just being forgotten as a child and fighting a bureaucratic system."

The Unloved was filmed in Nottingham, a city Morton compares to Naples. "I wanted to show it as a beautiful city," she says. And while Nottinghamshire County Council proved helpful, the county's social services department were less amenable. "Nottinghamshire social services blocked every single meeting. I wasn't allowed to talk to anybody. I said to them 'talk to me... read the script... I want to get this right'. They said no. Staff were warned off. Once again it's a culture of cover-up."

In the end, Morton says, she didn't require their assistance. "I didn't need to do much research because I'm very much active in the care system. I work for a charity called A National Voice (for children in care) and I'm an ambassador for Save the Children. I also have lots of friends who are residential social workers, who looked after me as a child. I was able to ask them lots of questions off the record."

However, she is fully aware that she is one of the lucky ones. She is in a happy and secure relationship with the film-maker Harry Holm, son of the actor Ian Holm, and the father of her 15-month-old baby Edie. Her nine-year-old daughter Esme was with the actor Charlie Creed-Miles.

"For anyone who's been in care, successfully coming through the system is nothing to with money or success; it's the ability to feel love and be loved in return."

'The Unloved', Channel 4, tomorrow, 9pm