Teenagers risk destroying their health in later life as a result of their obesity, drug taking and unsafe sex, doctors' leaders warned today.

The British Medical Association (BMA) called for urgent action to address the worsening trend in adolescent health, which it described as a "potential public health timebomb".

A report by the BMA's board of science, published today, recommends the creation of healthcare services specifically for teenagers, because their needs are often not addressed by services designed for younger children or adults.

The report, Adolescent Health, paints a bleak picture of the problems facing young people in the UK.

The number of overweight children has doubled in the last 20 years, with one in five 13 to 16-year-olds now classed as obese.

Rates of sexually transmitted infections (STIs) are soaring among 16 to 24-year-olds, with 60% admitting they do not use condoms. And as many as 10% of women aged 16 to 19 may be infected with chlamydia, which can make sufferers infertile if untreated.

Alcohol consumption is also on the rise, with some under-16s admitting drinking an average of 10 units of alcohol per week, equivalent to five pints of beer or 10 standard glasses of wines.

A quarter of 15 and 16-year-olds throughout the UK are regular smokers, while 11% of 11 to 15-year-olds in England have used drugs at least once in the past year.

In addition, one in five teenagers may experience mental health problems, such as depression and self-harm.

Vivienne Nathanson, the BMA's head of science and ethics, said: "Young people in Britain are increasingly likely to be overweight, indulge in binge drinking, have a sexually transmitted infection and suffer mental health problems.

"It is high time we provided education and healthcare services that target the specific needs of young people. We need to ensure that young people do not fall in between the gap between services for children and those designed for adults."

The reported recommended improving access to contraceptive services, banning alcohol advertising, reducing the availability of cigarettes and increasing their price. It also called for social skills training and anti-bulling policies to improve teenagers' mental health.

Dr Nathanson said sexual health services for teenagers were "almost non-existent".

"Access to services is key. Do we really expect a 15-year-old boy with gonorrhoea to take time off school to visit his GP and talk about his sex life? Surely it would be better to develop easily accessible services that are suited to his needs," she said.

Russell Viner, consultant in adolescent medicine at University College hospitals and Great Ormond Street hospital, condemned the lack of dedicated healthcare services for teenagers in the UK.

"Young people are often treated in children's or adult wards even though their needs are very different. The lack of dedicated services for young people in the UK is a scandal."

Dr Viner, one of the few consultants to specialise in adolescent health in Britain, also called for a more coordinated response to young people's needs.

"We need to develop a coordinated approach to adolescent health that involves healthcare, education, social services and youth justice system so that we can target all young people including those who may be most at risk such as young offenders, the homeless and people from deprived communities."

The BMA's report follows a stark warning from by England's chief medical officer, Professor Liam Donaldson, that the health of some children is so poor they could die before their parents.

The government is already considering moves to limit junk food advertising to children amid warnings of a looming child obesity "epidemic". Doctors are seeing cases of diabetes in children aged just 13 due to poor diet and sedentary lifestyle.

Ministers have launched several initiatives to tackle unhealthy lifestyles in recent years, including the "five a day" scheme to encourage people to eat more fruit and vegetables, smoking cessation projects, a sexual health strategy and a teenage pregnancy strategy. But, as yet, these have had little impact on adolescent health.