The unspeakable practice of female circumcision that's destroying young women's lives in Britain

"Promise you won't print my name or anything?" she implores repeatedly. "Promise no one will ever know that I've spoken to you? If people in my community find out, they'll say that I've betrayed them and I'll have to run away. And anyway, I don't want my parents to be sent to jail."

With great courage, this British-Somali girl - she asks that we call her "Lali" - is about to describe a barbaric act of ritualised cruelty which has been perpetrated against her. Knowing the danger to which she is exposing herself, her anxiety is entirely understandable.

For by speaking about it, Lali will break the ultimate taboo among Britain's 600,000 ethnic Africans. In Norway, where this brutal act is also prevalent, a young Somali woman was recently beaten, almost to death, for talking to TV documentary programme-makers.

It is known by a variety of names, the most common of which are female genital mutilation (FGM), female circumcision, or simply "cutting" - a word which somehow conveys the raw pain its prepubescent victims suffer.

Most people will be unfamiliar with this practice, which involves removing part or all of the clitoris, the surrounding labia (the outer part of the vagina) and sometimes the sewing up of the vagina, leaving only a small opening for urine and menstrual blood.

It is carried out for a variety of cultural reasons. Such is the secrecy that surrounds the practice that even those aware that it occurs in large swathes of Africa and Asia will be shocked to learn that it is prevalent in Britain.

During a highly disturbing, four-month investigation, however, we uncovered evidence that thousands of British-African girls, in towns and cities throughout the country, have been forcibly "cut".

By conservative estimates, 66,000 women and girls living in Britain have been mutilated. This figure, accepted by the Metropolitan Police, came in a report by a volunteer organisation funded by the Department of Health and carried out with academics from the London School of Tropical Hygiene and the City University.

And thousands more girls are at imminent risk as families club together to fly professional "cutters" from Africa to Britain.

These women "elders" perform the crude operation for up to £40 a time, often on kitchen tables or floors, without anaesthetic, using filthy, blunt knives, razor blades or scalpels.

Many readers will be distressed by our report, but this practice is an abomination which has no place anywhere, let alone in a civilised society, and if it is to be expunged then this is a story that must be told.

There is no way of escaping the unpalatable terminology, just as there is no way for girls like Lali to escape the unsterile knife which cuts them as they are held down and which will result in a lifetime of physical and psychological pain.

Some people say the practice is to increase the sexual pleasure of the man, but this is only one appallingly outdated reason why many womenfolk from 28 African and some Middle Eastern countries, most of which have sizeable representation in Britain, are treated like this.

It is also done to demonstrate their virginity on their wedding night; and because "uncut" girls with the ability to enjoy love-making are considered more likely to be promiscuous, unhygienic, and prone to diseases such as Aids.

Attempts are also made to justify this iniquitous practice on religious grounds. Some hard-line Muslims insist that women must undergo genital cutting to remain faithful to the purest teachings of Islam - although, in truth, it is not even mentioned in the Koran, and only ambiguously in the Hadith (a collection of oral traditions about the life of the prophet Mohammed).

Several leadings Imams have openly condemned the practice. This, though, does not deter its proponents, who maintain that it is their inalienable right to live according to their traditional beliefs and customs, rather than conform to British values. Indeed, some argue that the freedom to carry out FGM is a fundamental principle of our multi-cultural society.

Whatever the arguments, the fact is that genital mutilation is a reality, and the Metropolitan police is so concerned that it recently set up a special unit to investigate and prosecute the perpetrators. Heading the unit is Detective Inspector Carol Hamilton, herself a mother, who was horrified when she discovered what was happening to other people's daughters.

The Met team also educates regional police forces about FGM, and speaks to mosques, community groups and local authorities.

Usually their visits are well-received, but we found that at least one London council declined to publish material highlighting the suffering and danger the practice causes - for fear of offending ethnic African residents.

This kind of attitude incenses Detective Inspector Hamilton. "We are all becoming very culturally sensitive," she says. "People are a bit frightened of saying 'You can't do this here' because people shoot back with 'But it's our culture'.

"But it's not: this is just plain cruel. I won't be put off by the politically correct argument. We have to be seen to be strong on this. I don't care about human rights - I care about the rights of the child. Everything else has to go out of the window.

"We have one rule in child protection: the child is of paramount importance. I stick by that firmly."

Together with the Waris Dirie Foundation, an international campaign group formed by the Somali-born supermodel who suffered genital mutilation as a five-year-old child, the Met announced a £20,000 reward last July for information leading to the conviction of anyone who performs or abets cutting.

Under the 2003 Female Genital Mutilation Act, those involved could be jailed for 14 years. Yet the fact that no one has been prosecuted says much about the problems the police are facing.

"There are thousands of girls being cut in your country," says Waris Dirie spokesman Walter Hutschinger. "We are sure it's going on, and on a very big scale. Your law is one of the most comprehensive in the world, but it is useless if nobody will help to implement it.

"We have been contacted by girls from all parts of Britain - London, Cardiff, Sheffield, Birmingham, Liverpool, Reading, Slough, Milton Keynes, Crawley - anywhere there are big African communities.

"Many of these girls know they are about to be cut and are desperate for help, but they are even more afraid of what might happen to them if they come out in the open.

"One young woman wrote recently to tell us that she was about to be taken home to Somalia to be cut, and she was terrified because her older sister had died after cutting. [To avoid detection, the mutilation is often done in a girl's native country.]

"She was thinking of running away - but she didn't know where she could go or what she would do. The girl says genital mutilation has destroyed her family. We wrote back offering a meeting, but she has not been back in touch.'

During our investigation, we found similar difficulty finding girls willing publicly to condemn a practice whose "virtues" are impressed upon them from infancy so that they are effectively brainwashed into believing it to be an essential step towards womanhood.

Lali is so determined that other girls should be spared the misery she has endured since the cutter came to call four years ago that, last week, she bravely told us her story.

She was three years old when her family left impoverished, war-ravaged Somalia and settled in the East End of London, where her early childhood life seemed immeasurably better.

Everything changed for Lali when she was 11 years old. One morning, her mother told her, quite casually, that they were to visit another Somali girl, whom she liked.

"I thought I was just going to play with my friend, so I was happy," Lali says quietly, avoiding eye contact.

Soon after she arrived at the friend's anonymous council house, however, cold reality dawned. In fact, Lali's mother had secretly joined together with several other women to pay for a "cutter" to travel to London from Mogadishu to circumcise their daughters.

"They believed it had to be done, otherwise we would never get a husband,' Lali shrugs.

What happened next was like a scene from medieval times. Her mother, other female relatives and family friends suddenly grabbed Lali and grappled her to the floor. Then, on cue, the strange woman came in, like a torturer with her bag of implements.

"They held me down, and when the woman began cutting I screamed, so my friend's sister put her hand tightly over my mouth," she says. "I had known her and these other women all my life, and now they were doing ... this."

The cutting often results in life-threatening complications such as septicaemia, haemorrhaging or cysts, but in this respect Lali was fortunate. Outwardly, at least, she quickly recovered and returned to school, too frightened and ashamed to tell her teachers and friends about her ordeal.

However, the legacy of the atrocity inflicted on her when she was 11 years old will always remain. When a marriage is arranged for her, sex will be a painful duty to be endured.

If she is lucky enough to avoid the pre-natal complications frequently caused by genital mutilation and have children, she will almost certainly have to undergo a Caesarean section.

"It is the most traumatic rite of passage," says Comfort Mohmoh, a doctor who runs a Well Woman Clinic at London's St Thomas' Hospital and has performed a number of successful operations to reverse genital mutilation - a procedure possible only in less severe cases. She sees from 400 to 500 cases a year.

"These women get abdominal pains, backache, extremely painful periods, recurring urinary infections and, inevitably, a great deal of pain during intercourse."

Lali is already encountering some of these physical problems, yet in some ways the emotional and psychological damage is even worse.

"What happened to me has totally broken my trust in the women I loved," she told us. "I didn't believe my mother could let this happen. My love for her has changed.

"It hurt so much. I would never let my children suffer this. I don't believe this is right. It's a stupid, old-fashioned custom. Why can't we forget it?"

This alienation between mothers and daughters, of course, is another subtle way in which the practice subjects African women to male authority. Among the many otherwise educated and reasonable British-African men we spoke to, however, few were willing to call a halt.

With breathtaking sadism, their attitude was summed up by one man during an internet chat forum for Somalis living in Britain. "They should get their kintirs [Somalian for clitoris] cut off if they can't control their passions," was his message to liberated female compatriots.

One lone voice was Asif, a 26-year-old Somali mechanic who came to London at 15 - though his reasoning was hardly reassuring.

"We call these girls 'table-tops' because they are like wood," he told us. Rapping his fist on the table, he added: "Who wants to make love to this? I would never allow this to happen to my daughters."

As Detective Inspector Hamilton has discovered, however, he is very much in the minority. "I met one group of Somalis and got the message that cutting was even stronger here than in Somalia," she says. "Here, it seems, they feel the need to keep their traditions going.

"But detection is very difficult. If somebody rings and tells us a girl has been subjected to it, how do you check that? Especially when the family seem quite reasonable and say they don't believe in it, but refuse permission for the children to be medically examined."

Perhaps we should take a lead from France, whose methods of prevention have been strengthened following a landmark case in 1999, when a woman of West African origins was jailed for eight years for cutting 48 young children.

Now all French children of African background are closely scrutinised by social workers and doctors during infancy, and any abnormal behaviour or prolonged absence from school is immediately investigated.

It is also considered a duty of French doctors to examine any ethnic African girls they suspect have been mutilated and, waiving usual patient confidentiality rules, report their parents to the police if their suspicions are confirmed.

In this age of political correctness, no doubt, factions in Britain will argue that such interventionist activity is discriminatory and a breach of human rights. There will also be those who believe female genital mutilation to be an issue for the African community to resolve, arguing that our overstretched police and health professionals have more pressing matters to address.

Detective Inspector Hamilton was persuaded otherwise when she sat through a graphic video showing a cutter at work. With its haunting screams and bloodied instruments, this real-life horror film changed her life.

"These little girls shouldn't have to live in that other world," she says. "They go to school here. Their homes and friends are here. They are our little girls. They are British. What is happening to them is barbaric - and it must be stopped."

• Anyone with information about female circumcision should call Crimestoppers in confidence 0800 555111, or email david.jones@dailymail.co.uk