A Midland sex health clinic has warned teenagers against US-style virginity pledges, claiming they are more likely to lead to them catching sexually transmitted diseases.
The Brook clinic in Birmingham said youngsters who took a vow of chastity risked being ignorant about sexual relationships.
Chief executive Penny Barber claimed experience in the US showed such youngsters still engaged in sexual activities that did not lead to losing their virginity.
As a result they were less likely to use contraceptives which, coupled with their lack of knowledge, meant they had above-average rates of sexually transmitted infections.
" Abstinence education programmes tend to be 'absent education', with doctrine replacing facts," said Ms Barber.
"Where you have abstinence programmes then what you have is ignorance about sexual health.
"So people may indulge in other activities which they know may not get them pregnant, such as oral and anal sex, but not realising that by doing this you can catch sexually transmitted diseases."
She added: "You have a lot of double standards of young people pretending not to have sex and doing it without protection."
The Brook clinic, based in John Bright Street, wants sex and relationship education to be made part of the National Curriculum. It believes primary schoolchildren should be taught about puberty and menstruation before it happens to them.
But Ms Barber stressed she was not encouraging teenagers to have sex.
"Abstinence as a freelychosen lifestyle is just fine," she said.
"Sex and relationship education emphasises the importance of not participating in any sexual activity unless you genuinely wish to, and of ensuring any partner consents.
"But even if you wish to remain celibate what is the danger in understanding your emotions and physiology?
"I don't see how knowledge can be anything but beneficial, especially when young people are bombarded with information about how to be sexually attractive from an early age."
The danger of not providing good sex education to teenagers, warned Ms Barber, was that they would be left to be misinformed by " myths" spread by peers in the playground.
"It is no substitute for proper sex education," she said.
"That is why we are calling for sex and relationship education to be part of the National Curriculum.
"There is an obligation to do the biology bit as part of the science curriculum. What we are seeing is a trend for people to say therefore it is happening in schools. Well, not really."
Teenage pregnancy rates in Britain are the highest in Western Europe and among the highest in the world.
Latest teenage pregnancy figures for the West Midlands show there were 2,875 conceptions in 2003 - a nine per cent drop from 1998.
Of those, 42.7 per cent were terminated.
In Birmingham, there were 1,151 pregnancies in 2003.
Ms Barber claimed Britain's rate had changed little since the 70s, unlike many other countries in Europe where sex awareness programmes had been introduced.