Laura is plagued by thoughts of men. In her quest for a boyfriend, the 10-year-old hangs out at the Trocadero in central London wearing the skimpiest of miniskirts and a skintight boobtube.

With parents who play little part in her life, Laura is being brought up by older brothers and has little concept about personal safety and no idea at all about sexually transmitted diseases. 'I really, really love boys,' she said. 'This can sometimes be a problem. Once this boy I met at the swimming pool called Derrick asked me over to his house. I went to the address he gave me, but the door was opened by a big man who didn't know who Derrick was but who asked me to come inside anyway. I ran away because I was scared, but I still hope Derrick calls back because I really want a boyfriend.'

Laura's behaviour is not unusual: Chloe Ruthven, a learning mentor at the George Eliot junior school in north London, meets children like Laura all the time. 'That's mild,' she said. 'I hear incredibly alarming stories on an almost daily basis. These children live in a world of utter confusion, ignorance and endless rumours where parents are frequently almost entirely absent. If the schools can't save these children, then no one else will.'

But although Ruthven works as hard as she can, she knows she can't do it all. 'There is this gap between the home and the school, and in this space some desperately worrying and dangerous things are happening,' she said. 'The gap has to be closed: the school has to expand its grasp to catch these children, because otherwise they are just going to fall.'

The rate of sexually transmitted diseases is soaring in Britain in a way that has caught everyone by surprise. After the campaigns of the Eighties when the image of tombstones was used to warn people of the dangers of HIV, there was a substantial drop in infections as more and more men started to use condoms.

But the lessons have been forgotten and since the late Nineties the UK has seen rates steadily climb. The Health Protection Agency's last figures - to be updated this week - show astonishing increases between 1996 and 2002. For chlamydia, known as the 'silent epidemic' because it is often symptomless but can cause infertility in women, the rate has leapt by 139 per cent in that time; about one in 11 sexually active women are thought to carry it.

Another disease making a big comeback is gonorrhoea. The early symptoms include painful urination and discharge and it can be treated, but if not men get fevers, chills and swelling of the genitals and prostate. Rates soared by 109 per cent between 1996 and 2002, with particularly high rates in younger men. Even syphilis is increasing. It starts with a single, usually painless sore, but can cause organ damage, paralysis, blindness, dementia and death. According to the Health Protection Agency, there were 1,193 cases in 2002, a staggering 870 per cent increase over six years.

Much of the syphilis is acquired by young men having sex abroad, because of the distinctly laissez-faire attitude towards contraception. A study published in the British Medical Journal last week showed that, by sleeping with strangers, holidaymakers are exposed, in medical jargon, to different 'sexual networks' which are the ideal breeding ground for opportunistic infections.

A review of different studies of travellers with sexually transmitted infections showed that around one-third of holidaymakers in Tenerife had had sex with a new partner there. Up to two-thirds of them had not used condoms.

Researchers showed there was also a risk of more exotic diseases such as chancroid, or the human T-lymphotropic virus, which is prevalent in the Caribbean. Between 2000 and 2002, 69 per cent of heterosexually acquired HIV in the UK was the result of an infection from having sex abroad.

The Family Planning Association is deeply worried and believes that health services provide very patchy provision for testing and treating patients, let alone giving people advice about the risks. It thinks the future really lies in proper sex education from an early age which will be the only way that teenagers and others can be properly armed against them.

Anne Weyman, FPA chief executive, said: 'There is an enormous amount of ignorance out there about these infections. Britain doesn't have the proper sex education it should have. Every secondary school should have a teacher who is qualified to provide proper education on it, but the part that is compulsory is very narrow. It's just teaching about HIV and pregnancy, but you could cram it into one lesson for the whole of the curriculum. It should be far more talking about relationships and personal skills. Sex is governed by a set of attitudes and values, and just to teach the biology of it is to miss the point.'

One 14-year-old pupil in Leeds was shocked by the quality of sex education offered by her school. 'The biological information is pointless because we all know it already while the important stuff, like how to use a condom or deal with a boy who won't, or where to go if you need help, was crammed into half a lesson during which the teacher was reduced to tears because the boys were so mean to her,' she said.

'If my parents didn't talk to me about sex, I would be dangerously ignorant. There are already a few girls in my class who have had abortions and one who is pregnant. It is all through ignorance.'

This pupil's experience is all too common, says Anna Martinez, coordinator of the Sex Education Forum, the national authority on sex and reproduction education. 'What young people are telling us is that what is on offer is too little, too late and too biological,' she said. 'Puberty and reproduction are formally covered in science lessons, but everything concerning the emotions and realities of relationships is taught at the discretion of individual schools.

'Children tell us repeatedly that even the statutory part of the education passes them by because it is taught in isolation, outside the context of a relationship,' she added. 'What children tell us they want is more discussion about the emotional side of sex and where to go for help.'

But some parents, like Sarah Ashby whose six-year-old daughter attends her local primary school in Bridport, Dorset, feel strongly that children should have less, not more, sex education.

'Schools give children far too much information at too young an age,' she said. 'It is ridiculous teaching them about homosexuality and other details until they have come to terms with sexuality in its basic, straightforward form.

'I will take my daughter out of her sex education class like a shot if I see her education lessons going in this direction but I know that by doing so, I risk stigmatising her.'

Weyman insists, however, that overall there is enormous support for more sex education from parents. Her problem is that there is little clear research to show what works in persuading teenagers to have safer sex or no sex at all.

Part of the problem, some believe, is that Personal, Social and Health Education (PSHE) classes are out of sync with the reality of the lives of many children. 'The advice the government asks teachers to give students is laughably irrelevant to the lives they live,' says Mike Hardacre, equal opportunity director for the Secondary Heads Association, who recently retired as headteacher of both Northicote and Coppice secondary schools in the West Midlands.

Hardacre was director of an 'education action zone' from 2000 to 2002 that included a ward with a high level of child prostitution and the highest level of child abuse in the West Midlands. 'Where do you start making a sex education lesson relevant to children like that if it is coming from the assumption that pupils are part of a middle-class, nuclear family?' he said.

A study published last week looked at an experiment run by researchers from University College London on whether teenagers aged 16 and 17 leading sex lessons would be a help to children aged 13 to 14. It was thought that safe sex messages coming from their peers would have more impact than those coming from adult teachers. The study showed fewer girls went on to have sex before they were 16, but there was no effect on boys' behaviour. It also showed that the rate of unprotected first intercourse was the same: around 8 per cent of girls and 6 per cent of boys.

Michelle Seaton fell pregnant as a young woman because she didn't know what to do after a condom split. She now works for the Young Woman's Clinic in Great Yarmouth, going into schools to talk to girls about sex education. She was astonished by the girls' ignorance but delighted by their eagerness to learn.

'They love us because we're on their level and can talk their language,' she says. 'They have a whole different attitude to us: they don't cheek or try to embarrass us like they do with the teachers, because they know that we have been there and done it ourselves.'

Five real reasons to take precautions

Chlamydia

Infections Up 139 per cent from 1996-2002

Symptoms Majority of infections go unnoticed, although non-specific symptoms include vaginal discharge, cystitis, abdominal pain in women and penis irritation in men. Untreated, it can cause female infertility.

Treatment Diagnosed with a urine test and treated with antibiotics.

Gonorrhoea

Infections Up 109 per cent from 1996-2002

Symptoms Causes pain during urination and half those infected get an unpleasant yellow-green discharge. It can lead to infertility in women and in extreme cases can cause heart inflammation or meningitis.

Treatment Diagnosed using a swab test and treated with antibiotics.

Syphilis

Infections Up 870 per cent from 1996-2002.

Symptoms Causes painless genital swelling and a skin rash. In its final stages, up to 10 years later, it can induce blindness, personality changes and paralysis due to damage to the arteries and the brain.

Treatment Diagnosed via a blood test, or swabs taken from open sores. It is easily treated with antibiotics.

Chancroid

Infections Rare in the UK, but holidaymakers having unprotected sex in developing countries, where it is far more common, are becoming infected in greater numbers.

Symptoms Initial symptoms are similar to syphilis, but develop into a painful spreading ulcer on the genitalia. Untreated, the infection moves into the lymph nodes and causes swelling, tenderness and abscesses.

Treatment The infection can be diagnosed at a clinic and is treatable with antibiotics.

Human T-lymphotropic virus (HTLV)

Infections Estimated that 20 million people worldwide are infected.

Symptoms Transmitted through breast-feeding, blood transfusion and sexual contact. Most people have no symptoms but it has been associated with a slight increase in the risk of some forms of adult leukaemia.

Treatment Most diagnoses are made through blood donations, which are screened for HTLV. There is no recognised treatment for the infection.