Four years after her daughter disappeared in Portugal, she has revealed she is tortured by a belief an abuser is responsible.

In an interview, Mrs McCann, 43, describes the guilt she endures on a daily basis over her daughter's abduction.

Kate McCann, right, has written a book about the disappearance of  Madeleine, left, and hopes sales will fund the search for her daughter
Marriage strain: Kate and Gerry McCann. Gerry said: 'There were times when I thought she (Kate) would never get back to being the woman I loved.'

'I become consumed with it. It was torture for me. It was horrible, so vivid,' she said.

Madeleine was snatched from her bed in the McCanns' apartment at a resort in Praia da Luz, Portugal, on the evening of May 3, 2007, days before she turned four.

Her parents were dining with friends at a restaurant, fewer than 100 yards away, and regularly returned to the room to check on their three sleeping children.

But the last time Mrs McCann went to check she found Madeleine had gone.

In her forthcoming book, to be called Madeleine, she writes: 'When she was first stolen, paedophiles were all we could think about, and it ate away at us.

'The truly awful manifestation of what I was feeling was a macabre slideshow of vivid pictures in my brain that taunted me relentlessly.

'I was crying out that I could see Madeleine lying, cold and mottled on a big grey stone slab.

'The idea of a monster like this touching my daughter, stroking her, defiling her perfect little body, just killed me over and over again.

'I would lie in bed, hating the person who had done this to us ' the person who had taken away our little girl and terrified her. I hated him. I wanted to kill him.

Kate and Gerry McCann, pictured outside their house in Leicestershire, try to live as normally as possible for the sake of their children

Lost: Next Thursday marks Madeleine McCann's eight birthday. She went missing a few days before she turned four

She told the Sun newspaper how her worries intensified when she heard of other abductions involving children nearby. Mrs McCann from Rothley, Leicestershire, also discloses the pressures the ordeal put on her 12-year marriage to husband Gerry.

Immediately after the kidnapping, the couple struggled to cope with their loss and their feelings of guilt. And while she continued on a relentless search for their daughter, he admitted he needed to 'switch off at times'. Mrs McCann, a part-time GP before Madeleine's disappearance, said: 'Gerry and I were just holding each other and saying: 'We're not going to survive this.''

'I didn't know if I would ever get back to the person I was. I was conscious about the effect this had on Gerry. He needed me to be together and I just couldn't get myself there.'

Mr McCann added: 'There were times when I thought she would never get back to being the woman I loved.

Gone: Gerry McCann's daughter disappeared from her bed in an apartment in Praia da Luz in Portgual, pictured

Abused fear: Madeleine's mother Kate McCann has told how she is consumed by fear that her daughter was snatched by a paedophile

'I felt our family was being destroyed. It felt like a fight for survival. That's when I couldn't see a way out.'

His wife credits the support of a trauma consultant, who joined them in Portugal immediately, for the survival of their marriage.

She also said the strength of their two other children, six-year-old twins Amelie and Sean, helped them get through.

Four years after her abduction, Mrs McCann reveals the memory she has of her little girl is frozen in time and she finds it difficult to imagine her as an eight year old.

She has had three dreams of her, all of them describing a phone call she receives informing her that Madeleine has been found.

She said: 'There she is and I'm cuddling her. The thing is, it's so tangible. I can feel her, smell her, feel her snuggling into me, like she always did.

'She's there, I'm holding her, I'm so happy. And then I wake up. And of course she's not there. The pain is crippling.'

The couple hope sales of the book will raise '1million to continue funding the worldwide hunt. Mrs McCann said: 'Every penny we raise through its sales will be spent on our search for Madeleine. Nothing is more important to us than finding our little girl.

'Madeleine is still missing and there is still a lot to be done. Our efforts to find her are not diminishing. If anything, they are escalating.

'The need for a review by the authorities of Madeleine's case remains, and our desire to achieve this unwavering.'

But she complained: 'We have tried in vain to get the authorities to play their part but our requests have seemingly fallen on deaf ears.

'It is simply not acceptable that they have, to all intents and purposes, given up on Madeleine. We need the authorities to do more.

'We are still searching for her. Our small team continues to review all available information, even though we still don't have access to all of the information that the UK and Portuguese authorities have.'

The McCanns believe that Portuguese police, pictured at the apartment where Maddie went missing, have "given up" on the case

Snatching: This is the apartment from which Madeleline McCann was snatched in Portugal in May 2007

To the McCanns' intense frustration, the Madeleine police files have been officially abandoned.

Mrs McCann said it was 'incredible' that no police force was looking for Madeleine and there had been no formal review of the police evidence, despite this being 'routine practice in most countries, especially when a key piece of the jigsaw may have been overlooked'.

Mrs McCann wrote the book on the computer in her study over five months and said finishing it was a 'relief'. She turned down the offer of a ghost writer.

Friends say the McCanns' ordeal takes a daily toll on their lives, but the couple live as normally as possible for the sake of their children.

She is often seen with the children in the village, taking them to swimming and dancing lessons

Scene watch: Portuguese police officers on duty near the Ocean Club village where Madeleine disappeared in Praia de Luz. Despite a high-profile investigation she has never been found

Holiday girl: Madeleine McCann in one of the last pictures taken of her

Madeline McCann's twin siblings will be haunted by the tragedy of their missing sister for the rest of their lives, their mother fears.

Amelie and Sean were just two years old when Maddie was snatched from her bed while they slept only a few feet away.

And while the pair, who are now six and attending school, still talk about their older sister, Kate McCann says they are still too young to fully comprehend the situation.

She said: 'I am well aware, if God forbid we are still in this situation, that the pain and the anger and the upset will come as they get older and they realise what actually happened.'

Their mother revealed how she and husband Gerry have found it difficult to explain to the twins why they cannot see their sister any more.

She added: 'We've been as honest as we can. They know that Madeleine was stolen. They call the person who took her 'the naughty man'.'

Mrs McCann said the children  knew their sister had disappeared in Portugal.

'Amelie said, 'We went to Portugal and then we woke up and Madeleine was gone.' '

At the twins' school in Leicestershire, where Madeleine was due to attend, teachers try to keep their lives as normal as possible.

All the children at the school know what happened ' which in some respects has made the job harder. According to the McCanns, one new boy once said to Sean: 'Madeleine is dead, someone shot her.'

Sean later told his parents about it ' but handled the situation well, they said.

Mr McCann said: 'He was very matter-of-fact. He said no one knows where Madeleine is.'

His wife added: 'All the parents have been really supportive and I don't blame the child at all, they are only young.

'Children do say things. But I think Sean and Amelie have handled it brilliantly.'

The McCanns said they have drawn strength from the twins, who often comfort them when they are in need.

Dear God, no! The moment she knew Maddie was gone

Artist's impression: Based on witness accounts, an image of the abduction

Kate McCann has described for the first time ever the horrifying moment she discovered Madeleine was missing from her bed.

In her heart-rending new book, she tells how she went back to check on Madeleine and her two-year-old twin siblings, Amelie and Sean.

As she entered the apartment, she felt a draft and noticed the door to the children's bedroom was wide open ' but did not immediately realise a stranger had entered.

She said: 'When I realised Madeleine wasn't actually there, I went through to our bedroom to see if she'd got into our bed. That would explain the open door.

'On the discovery of another empty bed, the first wave of panic hit me. As I ran back into the children's room the closed curtains flew up in a gust of wind.

'My heart lurched as I saw now, that, behind them, the window was wide open and the shutters on the outside raised all the way up. Nausea, terror, disbelief, fear. Icy fear. Dear God, no! Please, no!'

Madeleine's bed-sheet still had the corners neatly turned over ' and her Cuddle Cat soft toy and pink princess blanket were still lying where she had been sleeping.

Dashing over to the other two beds, Mrs McCann said she found the twins sleeping on obliviously. She then spent 15 seconds frantically searching the cupboards, wardrobe and bathroom of the apartment ' but admitted she already feared Madeleine had gone.

Mrs McCann then ran down to the rest of the party shouting, 'Madeleine's gone! Someone's taken her!' As everyone rushed back and began to search, Mrs McCann ran into the car park yelling her lost daughter's name. In extracts printed by The Sun, she tells of how windy it was, and says she kept imagining how cold Madeleine would be in her short-sleeved  Eeyore pyjamas, and wishing she'd had her warmer Barbie pyjamas on.

Recalling how fear was 'shearing' through her body, she said the party raised the alarm with the Ocean Club, where they were staying, at about 10.10pm, and asked them to call the police ' who did not arrive immediately.

When Mrs McCann went back into the room to check on the twins, she was surprised to see them still sleeping ' which made her suspect that they could have been sedated.