Nearly a third of 16 to 24-year-olds lost their virginity below the age of consent, a survey has suggested.
Nearly a third of young people had sex before the age of consent
The BBC Radio 1 poll also suggested 43% of young people had had at least five sexual partners with one in five having more than 10.
Over half - 57% - claimed to have had a one-night stand.
But many of the youngsters, who made up two-thirds of the 29,623 who responded to the online poll, said they did not always use condoms with new partners.
Some 38% of young people do not always use a condom with a new partner, with being too drunk cited as one of the most common reasons.
Alcohol was also strongly linked to a young person's first experience of sex, with 37% saying they had had a drink before having sex for the first time.
The survey, carried out in conjunction with BBC 1Xtra, Durex and MTV, also revealed deficiencies in young people's sex education.
One in 10 claimed to have had no sex education at school, while three quarters said they only learned the basics.
Many showed a lack of awareness about contraception failure, with 43% not knowing it was possible to get pregnant if a condom is not used correctly and 35% unaware that the contraceptive pill can also fail.
KEY FINDINGS 16-24-YEAR OLDS
30% lost it before age of consent, 4% before 14, 4% had not lost their virginity by 25
21% had one, a 33% two to four, 16% five to seven, 8% eight to 10, and 18% over 10
Men: 87% heterosexual, 6% homosexual, 4% experimented, 3% bisexual
Women: 82% heterosexual, 11% experimented, 5% bisexual, 2% homosexual
Asked what their biggest worry was regarding sex, 41% said pregnancy, 24% said HIV and 22% sexually transmitted infections.
However, the pressure young people feel to have sex appears to be declining with 23% of women under 18 saying they felt pressured, compared to 33% of those 32 and over.
Just 4% of the young people quizzed said they had not lost their virginity, the same number as had had sex before 14. Some 9% had had sex at 14 and 17% at 15.
Respondents in Wales and south west England tended to lose their virginity earlier, while Londoners and people from Northern Ireland lost it later than the average.
Men aged 16 to 34 were more likely to describe themselves as homosexual - 6% compared to 2% of women.
But 11% of women said they had experimented, compared to 4% of men.
A spokeswoman for Brook, the sexual health charity for young people, said: "In many respects these findings are not surprising, but they are still worrying.
"What it shows is how important it is to provide young people with good sexual education.
"But unfortunately much of the teaching in schools is too biologically-based."
Vicky Field, of the HIV charity, Terrence Higgins Trust, agreed. She said: "Without changes in the way we talk to young people about sex, rates of sexually transmitted infections will continue to increase dramatically."
A Department of Health spokeswoman said the government was trying to improve sex education and access to sexual health clinics.
She added: "We cannot tell people how many sexual partners they should have, but we do know that the more sexual partners a person has the greater the risk from STIs and unintended pregnancy.
"Teenagers who have talked about sex and relationships are more likely to delay the age when they first have sex and are more likely to use contraception and be responsible in their relationships."