The research, by the Health Education Authority, also found that a third of pupils aged between 14 and 16 have used cannabis.

More than a quarter of pupils in the 14-16 age group believe taking the Pill will protect them from sexually transmitted diseases, while around the same number think that having a steady partner will do so.

The survey also shows that many 15 and 16-year-olds are ignorant about a number of diseases including syphilis, gonorrhoea and chlamydia.

Some teenagers believe the Pill can prevent disease

The figures revealed on Friday have caused concern about the quality of sex education in schools.

Almost 10,500 children aged between 11 and 16 were questioned for the survey. Questions about attitudes to sexual health and drug-taking were put to the older pupils.

All children taking part in the survey were asked about attitudes to other topics including school and family life, smoking and drinking.

While 92 per cent of the 14 to 16-year-olds were aware of HIV and AIDS, just one third had heard of syphilis, 39% of gonorrhoea, 51% of herpes and 14% of chlamydia.

But one in six 15-year-old boys claimed to have heard of a non-existent sexually-transmitted disease called 'gonaditis', which was made up by researchers.

Disease increasing

The statistics emerged as a BBC Panorama documentary this week revealed that reports of gonorrhoea in teenagers aged between 16 and 19 rose 46% between 1995 and 1997.

Cases of chlamydia, which can make women infertile, increased by 56%.

Teenage pregnancies in England and Wales increased in 1996, bucking the trend in the rest of Western Europe.

The rate of 63 per thousand in 1996 was double the rate in Germany, four times the French rate, and seven times the rate in the Netherlands.

Juliet Hillier of Brook Advisory Centres, the young people's sex advice charity, said the results of the survey were worrying, and showed that schools needed to improve their sex education programmes.

"It's a worrying illustration of how far schools have to go to improve education and information for young people," she said.

"We come across this lack of knowledge in our everyday experience as service providers to young people.

"We would really like to get the message across that it's vital to educate young people. Sex education in schools needs to go a lot further so that young people have the information they need to make sensible choices."

'No surprise'

Kathy Elliott, a director of the Health Education Authority, said the figures were not a surprise and admitted that in some aspects of sexual health, young people did not have as much knowledge as they needed.

But she said that some adults were also lacking in knowledge, and said that the responsibility for educating children in sexual health should not fall solely on schools.

"Schools are one source, but children also get their information from their parents, the media, friends and brothers and sisters," she said.

"Sometimes people think schools ought to do it all, but we all have to do our part. Schools are one part of the picture."

Working on improvements

The Health Education Authority was working with the Healthy Schools Initiative to improve all aspects of health education in schools, she said.

And an Internet Website called 'Wired for Health' which was launched on Thursday to supply teachers with information about children's health would help. The survey also shows that:

• Half of all young people said they had been bullied at some time during their time at school
• 22% of girls smoked, compared with 16 per cent of boys
• 30% of pupils aged 14 to 16 had tried cannabis

Nearly a quarter of girls smoke

But although alcopops were named as an increasingly popular choice of drink among young people, the survey shows that overall alcohol consumption has not increased in the last three years.

One in five children questioned said they did not drink alcohol, and three-fifths said they only drank a little.

Researchers found that nine out of 10 children felt generally happy about their lives, and the same number considered themselves to be 'quite' or 'very' healthy.

The survey is based on fieldwork carried out in 1997, and is part of a rolling study by the World Health Organisation of attitudes towards health among young people in 29 countries.