The thundering knock came early in the morning. It was 6.30am. Without waiting for an answer the security chain across the door was smashed from its fittings. Feet thundered up the staircase. The five children, all under the age of 10, were alarmed to be woken from their sleep by the dozen burly strangers who burst into their bedrooms, switched on the lights and shouted at them to get up.

This is not a police state. It is Manchester in supposedly civilised Britain in the 21st century. There is a clue to what this is about in the names of the children: Nardin, who is 10; Karin who is seven; the three-year-old twins Bishoy and Anastasia, and their one-year-old baby sister Angela.

Their parents, Hany and Samah Mansour, are Coptic Christians who fled to the UK after a campaign of persecution by a group of Islamic fundamentalists in Egypt whose friends in the secret police tortured Hany. But even though six Coptic Christians were shot dead by Muslim extremists only last week in a town not far from their home, the British Government has decided that it does not believe them. And so Britain's deportation police have launched another of their terrifying dawn raids on sleeping children.

Neighbours, awoken by the noise, tumble out bleary-eyed into the street, to find out what is going on. They look on, visibly shocked, as the family they have come to regard as friends in the tight-knit community of Moss Side over the past four years are bundled into vans and taken away.

"They woke the children up; they didn't even allow my wife to do it," says Hany Mansour. "They gave her a few big laundry bags and told her she had 30 minutes to pack. She and I were not allowed to talk to one another. They kept me downstairs. When she was brought down they took me upstairs. The most scary thing as that when we were put in the vans my wife and I didn't even know if we were being taken to the same place."

***

No one knows how many children have been snatched from their beds in this way in Britain in the past year. But the Immigration Minister Phil Woolas admitted in a letter to a concerned MP recently that more than 1,300 children were detained at three immigration removal centres in the UK during the 15 months between July 2008 and September 2009.

Some 889 children have been detained for more than 28 days in the past five years. In each of those cases an immigration minister or a judge had to sign a new authorisation every four weeks for their continued detention. The UK now has one of the worst records in Europe for detaining children.

"Are we in prison, Dad?" 10-year-old Nardin Mansour asked her father, when they were taken into a police cell block in Birmingham, where they had stopped for a lavatory break on their way to a deportation centre near Gatwick Airport. Around her were prisoners in handcuffs.

"No, we are not prisoners," Hany told his daughter. But she could be forgiven for not believing him.

The immigration centre which was their final destination was Yarl's Wood in Bedfordshire. It is surrounded by massive fences topped with barbed wire. Its staff wear uniforms. Child inmates have to pass through between eight and 10 locked doors. The children, many of whom are under the age of five, are photographed and fingerprints can be taken. There are body searches – even of Nardin's one-year-old baby sister – and frequent roll calls. Children are required to carry identity cards with them at all times.

All of this does untold psychological damage, according to the Royal College of Paediatrics and the Royal College of Psychiatry. Last month they joined with the equivalent body for GPs to warn that the detention of children and their families caused "significant" serious physical and psychological harm to children who are already among the most vulnerable members of the community – and who require special and humane treatment but are being accorded the exact opposite.

"All the young people I have been talking to have lingering effects, after months and even after years," said Sheila Melzak, a consultant child psychotherapist who has worked with families in detention, at the time the three colleges made their call for the detention of children to be ended. "It is frightening for children to see their parents in tears," she added. "They see adults in a high state of stress, they hear a lot of shouting and crying. It is a highly institutionalised environment and that leads to problems with eating and sleeping and learning."

A copy of the research on which those anxieties were based has been passed to The Independent. It is the first study of its kind in the UK into the mental and physical health of 24 children held within a British immigration detention centre.

It shows that every single one of the children seen in Yarl's Wood by a team of paediatricians and psychologists displayed some signs of distress and 73 per cent of children they examined had developed clinically significant emotional and behavioural problems since being detained. None had previously had such problems.

The study's lead authors were the consultant paediatrician Dr Ann Lorek, of the Mary Sheridan Centre for Child Health in Lambeth and the clinical psychologist Dr Kimberly Ehntholt of the Traumatic Stress Clinic in Camden and Islington NHS Foundation Trust. It catalogued symptoms of depression and anxiety in every child they examined. All the children seen by clinical psychologists presented as being disorientated, confused and frightened. More than half, who had previously been well behaved at home and in school, had developed conduct problems.

They had been affected by a combination of factors, Dr Ehntholt believes, "including a recent deterioration in their parents' mental health, increased fear after being suddenly placed in a detention facility, anxiety over returning to their country of origin where they may have experienced traumatic events, as well as the abrupt loss of home, school and friends".

Eight children had lost weight since entering detention; a two-year-old and a nine-year-old had both lost 10 per cent of their body weight. Three were refusing to feed themselves or would only take milk. Five children had begun bed-wetting and one was also soiling herself in the daytime since being detained. Four had manifested a regression of language since entering detention, including one child who had become selectively mute.

The problems the children displayed included post-traumatic stress disorder, depression, anxiety, nightmares, refusal to sleep except in bed with a parent, changes in appetite and somatic symptoms like headache and stomach pain. They showed a loss of previously-acquired cognitive skills and had developed particular problems with peer relationships.

Children were distressed at missing "real school" and at being unable to take important exams, says the study. Many also missed important hospital appointments.

"The emotional well-being and health of many detained children is extremely vulnerable and likely to deteriorate further if exposed to additional stressors or traumatic events," the study says. "The risk of exposure to additional stress is high within immigration detention centres where riots, violence, hunger strikes, and incidents of deliberate self-harm, including deaths due to suicide, have been reported." One man committed suicide on his first night at Yarl's Wood in the desperate hope that his 13-year-old son would then be allowed to remain in the UK.

But this is not the only damning evidence. Before they were sent to Yarl's Wood, the Mansour family were detained for 18 nights at Tinsley House Immigration Removal Centre near Gatwick, despite the fact that the place has no real facilities for the detention of children. On 18 December last year, the Chief Inspector of Prisons, Dame Anne Owers, published a highly critical report into Tinsley House after an unannounced visit to the centre at the time the Mansours were there.

"The arrangements for children and single women were now wholly unacceptable," her visit revealed. Indeed, things had considerable worsened since the inspectors' previous visit. Children continued to be detained for more than 72 hours. They had limited access to fresh air. Childcare and education arrangements had deteriorated because trained and dedicated staff had left. There were continuing worries about children's safety in a largely adult male environment. The conduct by some of those who escorted inmates for deportation was unprofessional. "Unnecessary force" had been used on children while removing one family.

"Overall, this is a deeply depressing report," the Chief Inspector concluded. "It is a wholly unacceptable state of affairs."

It followed a report on Yarl's Wood by the same inspectorate which concluded that "there was no evidence that children's welfare was taken into account when making decisions about initial and continued detention". It highlighted the case of a child with a broken arm who was left in pain for more than a day before being taken to hospital, children with sickle cell disease being denied painkillers, children who were separated from their parents and the handcuffing of one adolescent child.

***

Defenders of this system say that since Britain wants to place limits on immigration to ensure that foreigners don't abuse our asylum system it is inevitable that children are locked up. "If people refuse to go home then detention becomes a necessity," the Border and Immigration Minister Phil Woolas has said.

Yet it is incontestable that Government policy has become more draconian here. Under the rules in force in 1998, official policy was that children under 18 should only be detained "as close to removal as possible so as to ensure that families are not normally detained for more than a few days". But in October 2001 the Government changed that rule to allow detention without time limit. Earlier this year planning permission was given to double the capacity of Yarl's Wood.

Those charged with implementing the policy insist the system they run is "humane and compassionate".

"We would much rather that those families found not to need international protection leave the UK voluntarily," Jo Liddy, the regional director of the UK Border Agency in North West – the area responsible for the handling of the Mansour family – was quoted as saying in the South Manchester Reporter. "Where people refuse to leave, however, it is our responsibility to enforce the decisions of the courts and send them home. The decision to detain a family before removal only happens as a last resort, keeping the family together. Where an enforced removal is necessary these are undertaken with extreme care treating those to be removed with courtesy and dignity."

Friends and supporters of the Mansour children find those words laughable. "There is not much courtesy or dignity in seeing a family of young children lined up in the street waiting to be taken away," says Jackie Tarpey, chair of governors at the school four of the Mansour children attend, Our Lady's RC Primary in Whalley Range, Manchester. "It is shocking that the Home Office is trying to forcibly deport a family with five young children in this way. Four of the children were born in the UK. No family should have to go through the ordeal that the Mansours are being put through."

Talk to Hany Mansour and you get some idea of the extended nature of that ordeal with its ritual of tiny humiliations.

In his quiet voice, the man who ran a prosperous shop in Luxor in Egypt before he was driven out catalogues a long list of little indignities: officers entering the house without waiting for him to answer the door; not allowing him to speak with his wife; not permitting his wife to wake the children; not allowing him to help her pack; forcing the children to leave behind treasured possessions; putting them in separate vans and not telling them where they were going; taking his mobile phone from him; not permitting him a phone call from the house.

On the petty limitations went. At the detention centre the children were body searched. "They even searched our one-year-old baby," he recalls. "When I asked why, they gave no answer. Officials asked inappropriate questions of him – whether he had been imprisoned, hurt or tortured, about whether he used drugs – in front of his children.

After three weeks at Tinsley House the family were taken to Gatwick to be put on a plane to Cairo. "On the way to the airport we were not allowed to sit next to the children," he says. "A different woman officer, with a bag of sweets, sat next to each of them trying to make friends with the child. But it didn't work. The children started crying as soon as they saw the plane.

"Ten minutes before take-off the senior officer asked me to get on the plane. I told him it was dangerous for us to go back to Egypt. I said:,'I don't want to go. I'm not going to resist. But I don't want to go, and I will tell the pilot that.' So he asked the children if they wanted to go and they said 'No'.

"Then he said he could use force on me but not on the children and asked me to persuade them. I said I wouldn't. So he turned the bus round. He wasn't angry but the rest of the team were. One of them said to me, 'So what's your next plan?' I didn't answer. I just said, 'Please leave me alone, I'm tired.' On the way back all the children fell asleep; they were emotionally and physically exhausted."

Next day the children asked if we were going home now. "But I couldn't tell them. Then letters arrived from the children's classmates, and books from the school. My children were crying hard as they read the letters."

Nardin went to phone Childline and asked for help. "She had a long talk to them but in the end they told her there was nothing they could do. She put the phone down sadly and asked if there was anyone else she could ring but I steered her away from that and said, 'No, let's leave it just now.'"

A week later a judge directed that the family should be freed and allowed to return to their home in Moss Side. "The children didn't jump for joy that first time," their father recalls. "They were just bewildered."

***

It is easy to agree to the idea that illegal immigrants must be removed from Britain. But need this involve treating children with such callous indifference and even cruelty? The idea of dawn raids by state officials on people's homes smacks of the kind of police state from which Britons instinctively recoil. Political pressure is now building for an end to imprisoning children in immigration centres.

The call by the Royal Colleges of Paediatrics, General Practice, and Psychiatry for an immediate end to the practice echoes other moves. The Children's Commissioner, Sir Al Aynsley-Green, has conducted his own investigation into Yarl's Wood, which painted a shocking picture of neglect and even cruelty towards children trapped behind the state's razor-wired walls – with claims of officers laughing and making fun of inmates when they showed signs of distress or anxiety.

He too concluded that there is "substantial evidence that detention is harmful and damaging to children and young people" and said it was "extremely worrying" that more than one in three children was being held for longer than 28 days. More than half were eventually released, suggesting their detention was unnecessary.

In the House of Commons 105 MPs have in the last few weeks signed an early day motion put down by Chris Mullin calling for an end to locking up children, noting that families with kids are among the least likely to abscond and that other countries have alternative solutions than the locking up of innocent children.

One of the signatories, the Liberal Democrat MP Dr Evan Harris, has been campaigning for three years through the Commons Joint Committee of Human Rights on alternatives to detention – such as tagging or daily reporting to a police station. "The detention of children is absolutely wrong. It is unnecessary, unethical and a waste of public funds," he told The Independent. "It is shocking that the UK is the only country in Europe that allows the indefinite detention of children ... in this prison-like environment." His party leader, Nick Clegg, has accused the Prime Minister, Gordon Brown, of "moral cowardice" for allowing the immigration authorities to continue to inflict what is "in effect, state-sponsored cruelty ... behind a veil of Government secrecy."

***

Five months after the Mansour children were freed, the immigration police struck again. This time the knock at their Moss Side home came at 6.15am. Again UK Border Agency officials entered the Mansour home without waiting for the door to be opened to them. "They didn't give me chance to open it," Hany Mansour reveals. "When I got downstairs they were in the house already. I told them I had put in a fresh claim for asylum with a new lawyer who hadn't been informed that it had been declined."

"Here's the letter rejecting it," the lead officer said, giving them this time two hours to pack their entire life into a few chequered laundry bags.

Many of the Mansours' neighbours and a large number of parents at the children's school insist that a miscarriage of justice has been perpetrated here. Hany, a Coptic Christian, had fallen out with some Muslim business associates and had then been subjected to a campaign of persecution by a group of Islamic fundamentalists who burned his car and destroyed his house. When he went to the police to complain, he says, he was arrested and charged with insulting Islam. He was detained in solitary confinement for 17 days and tortured. On his release the family fled, leaving all their belongings behind. The local Coptic bishop paid for their flight out of Egypt.

His claim was corroborated by the medical evidence of a doctor in the UK who examined him on his arrival in Dover." The court didn't challenge the medical evidence that he had been tortured," says his new solicitor Anita Vasisht, a partner at Wilson & Co Solicitors in London, who has now successfully applied for a judicial review of the case. "In Egypt he had a boat, a bookshop and a busy shop in the Hilton hotel," said Kim Draper, a parent-support adviser at the Mansour children's school. "Why would he want to give all that up and come and live in Moss Side if he wasn't being persecuted?"

The school and the neighbours mounted an effective campaign on behalf of the family, raising a 2,000-signature petition to testify to the support of the local community for the Mansours – and using Facebook and the internet to flood the Immigration Minister Phil Woolas with pleas to allow the family indefinite leave to remain in the UK. The campaign has been a double-edged sword, raising fears that the public attention would make the Mansours even greater candidates for persecution by Muslim extremists if they are eventually put on a plane to Egypt.

But it has all been so embarrassing for Government ministers that Home Office lawyers were instructed to ask a judge to expedite a rejection of Hany Mansour's application for a judicial review. "Clearly, they were hoping to bundle the family out of the country quickly, specifically because of the media interest in the case," his lawyer, Anita Vasisht, says. "It was a cynical political act and really shoddy behaviour." The judge refused the Home Office challenge and a judicial review of the Mansour family's case will proceed in the coming weeks.

But whatever the technical rights and wrongs of Hany Mansour's asylum situation, it is hard not to see the way the Mansour children have been treated as an affront to the traditional British sense of decency. Four of the five children have been born in the UK. They are entirely blameless victims whose human rights have been grossly infringed and who have already been significantly damaged by what has happened to them.

"These children are witnessing their parents in an extreme state of fear," says Anita Vasisht. "They are very afraid of what might happened to them if they go back to Egypt." Added to that is the disorientation of being snatched from their beds by strangers not once but twice. The impact of all this is clear to the children's teachers.

"Nardin was a lovely gentle little girl, quietly confident," says her teacher, Audrey Land. "She was a model pupil, happy, with lots of friends, the kind of child you would give extra responsibilities. The change in her has been massive.

"Nardin doesn't share her feelings; she internalises a lot. But if I raise my voice at all she starts to cry. She's been aggressive with other children, which isn't like her, then she gets upset at her own behaviour. Before, she would play with anyone, but when another child touched her she went hysterical just as she had with the immigration officers at the airport, shouting, 'Nobody touch me!'

"I'm quite horrified at some of the things she's seen and the questions that have been asked of her parents within the child's earshot. She knows she's been manipulated by adults. She's taken on the role of an adult in her attitude to her little brother and sisters. She has talked about how she thought of killing herself, which is neither the appropriate experience or vocabulary for a child of 10."

Anna Ward, who teaches Nardin's seven-year-old sister Karin, has seen other kinds of distress. "Since she came back she is very different," she says. "Before she was up for anything new but now she's reserved and easily upset. She's very very tired. She's emotionally exhausted. There's a massive difference in her. She looks worried all the time. It's really hard to coax a smile from her and she's bitten her nails right down to the skin."

Karin had returned to school just before Christmas when the family were released after their lawyer lodged the application for a judicial review. The day before she had been snatched in the dawn raid she had been cast as Mary in the school nativity play. "She was thrilled," recalls Anna Ward, "but the next day she had gone."

Her teacher and a group of her pupils phoned her in the detention centre and told her we were keeping the part for her. "I had asked another girl in the class to read the part while Karin as away," her teacher said. "The day before the performance I came into the class and found that girl sitting on the floor crying. When I asked her what the problem was she said, 'I don't want to be Mary. I want Karin to be Mary.'"

When a family is ripped so brutally from their home it is not just those who are carted away by the police to whom an injustice is done. Something is rent in the very fabric of the community. "The second time they were taken away was very disturbing for the rest of Karin's class," said Anna Ward. "The other children were all crying they were very shaken by it. It was as if they didn't know who to trust."

"Everyone was more shocked the second time because we thought it had been sorted," said Kim Draper. "But if you look on the website of the National Coalition of Anti-Deportation Campaigns you can find families this has happened to not just twice – but eight times." Justice, in cases where children are involved, needs to be tempered by mercy, but that is a quality that is in short supply thanks to New Labour's pandering to the right wing anti-immigration lobby.

What would happen, I ask 10-year-old Nardin, if the family gets another sunrise knock on their front door. She cuts me off, mid-question. "Don't say knock," she corrects me, "because they don't knock. They just smash the chain off the lock and march in."

What kind of country allows that happen to innocent children as they sleep in their own beds?

Mine, I'm ashamed to say.

Nardin's story: "The next time they came to take us away they were very angry. You could tell" "First they break the door. Then they just run in up the stairs making as much noise as possible. Then they put the lights on to wake you. You are scared to see these people just there in front of you in your bedroom. They were freaky looking, they have a belt with handcuffs on and those police sticks – truncheons. There were loads in the room, about 10 of them.

They said: "Get dressed because we are going to take you to our office." I went to the bathroom but they told me I had to leave the door open and I wasn't allowed to open the window – they didn't say why but it was because they don't want you to escape.

I went downstairs. My dad was there . He said everything would be OK but they wouldn't let me go into the kitchen because it has windows.

Then I went outside the house and I had to go in a van. Dad was put in a different one, surrounded by these people. Mum looked very worried but I told her Dad had said everything was going to be alright.

When we got there you had to take off your shoes and coat and they took my dad's phone off him. But they gave him another one which didn't have a camera on it – you aren't allowed to take pictures inside the detention centre because they don't want people to see what it's like.

The second time they came to take us away they were really angry. They didn't say but you could see by their face. Dad told them that my brother had just had an operation on his hand and my sister had an ear infection and was waiting to go to hospital. But they took no notice.

On the coach I felt sick three times because of all the travelling. You're not allowed to sit next to the door.

We got there and there was this massive fence as big as a house with all curly wire on the top. When you get in it's like all empty space with nothing and then another big fence. Then we had to go through a lot of doors. They lock each one behind you. Inside, on the other side of the fence, there is a pretty garden out there but you are not allowed to go in it even though it has a big wall around it.

We went in a room with three sofas and some toys but most of the toys were broken. It was mainly baby stuff. They gave us colouring books but I'm too big for that.

They told my mum and dad to take some stuff out of all our suitcases and put it in one bag. We were allowed the keep one bag and the rest of our things were put away in a storeroom.

You had to stand in a line and have your photograph taken. I didn't smile. If I had known what was going to happen I would have stuck my tongue out. They use the photograph to give you an ID card.

Then we had to go to the nurse. She asked my dad: "Do you drink drugs?" And he said, 'No'. She asked him if anybody had ever attacked or hurt him. I don't know why. It was all confusing. At first they were nice and then they were asking you all these silly questions. And the lady from the nursery didn't change Angela's nappy.

They gave us three rooms but one was stinky, and dirty on the floor. There were windows in the room but they only opened a tiny bit so we slept two in a bed in the other rooms. The bed was made of wood. It didn't have a proper mattress so you couldn't bounce on it.

You could see rabbits out of the windows, that was the best bit, but I felt really confused and worried. They were nice to me but sometimes they treated my parents different from me. One woman said very bossy to him: "If your child goes out again I'm going to lock the door." He said: "She's just gone to the toilet; don't get angry till you know the full story."

There was a school there but you didn't get proper lessons, just colouring and painting. The teacher was Miss Jen. She asked us what score we would give Yarl's Wood out of ten. I said zero. She said how can we improve. I said you can improve by being nice to people and treating them all in the same way. Actually I didn't say that to her. I said it to my friend Vivienne but she wasn't there long because she was sent to Kenya. She didn't want to go because she had loads of friends and a nice school.

Vivienne was nice but some of the children there were mean to me and used to push me and say horrible things. One boy, who was 14 or 15, said he was going to get a stone and kill one of the rabbits on the other side of the fence. I said "Why?" And he started shouting. He threw the stones but he missed. But he kept throwing stones down the hole where the rabbit had gone. He was angry. A lot of people were angry.

They said: "Do you want to help decorate the Christmas tree." I said: "No, I have already decorated my own tree at home. We did it the day before they came and took us away."

They try to be nice to you to make you think that nothing is going on wrong.

Some presents came. [An Anglican priest dressed as Santa took them to the centre as a protest against children being locked up in immigration centres.] There was a big sack. They said you have to show your ID card and you get one present and one coin. It's a funny Santa if you have to show an ID card.

They keep saying to you: "Are you ready to go to Egypt? Egypt is a nice place, a wonderful country." I said: "No, I want to stay here with my friends, at my school to get a good education." They are trying to make you say the opposite of your Mum and Dad, they try to divide you up from them. She was trying to, but she was not very good at it.

I felt really angry. I said: "No way, I can do whatever I like with my own life." I thought: "Why is she doing this?"

When we were in the bus on the tarmac at the airport they said: "Do you want to get on the plane?" And I said: "No." And she said: "Well we can always come back next week."

Then a judge said they had to let us out. When I heard I said: "I'm free, I'm free." I was so happy, I tried to bounce on the bed but you can't, it's too hard.

When I got back to school I was very happy and all my friends were hugging me – just the girls – the boys just said hi – but my sister Karin got hugged by the boys as well in her class. A boy said: "I've kissed Karin; I'm glad she's back." One boy said to me: "You're lucky, you missed school." But I said to him: "I'd rather have been here, even doing maths."

Karin knows what's going on. The last day she said: "it was nightmare but it is over." But I'm thinking now that maybe I should come to school very early every day before these people can come and wake me up to take me away again.

When you wake up in your bedroom at home you should just see your wardrobe and the mirror, not a load of freaky people stood looking at you.

If it happens again I'm going to complain. I'm going to write them a letter to say: "Why are you doing this. I can stay in this country if I like. Who do you think you are? You are not in charge in this country." If they don't stop I will write to the Queen because I don't want to go to Egypt. Last time I was so fed up that I wanted to throw myself out of the window. The Queen is nice because I have read it in The BFG. I'll tell the Queen these people get money for being mean to people.