On Fridays, a seminar room on the fourth floor of the Islington sixth form centre is turned into a sexual health clinic run by the London Brook Advisory Centre.

Centre manager Michelle Telesford puts out a rack of leaflets on cystitis, safe sex and condoms, and props open the door. The radio plays The Cars’ “Who’s gonna pick you up, when you fall?”, and a packet of chocolate biscuits stands on the table beside a transparent plastic model of a uterus. The clinic - staffed by a doctor, a counsellor, and a sex educator - serves students aged 16 to 20.

“Because we run it in a very friendly, informal way, there isn’t the anxiety and embarrassment factor of being in a waiting room,” says counsellor Joanna Brien.

Brook believes that such non-clinical settings encourage young people to use its services, and convey the message that they offer information, advice and counselling, as well as contraception. There are no appointments and complete confidentiality.

Donna - not her real name - is 18 and is the third client of the afternoon, after a boy who wandered in for some condoms, and a young woman who had a pregnancy test in the consulting room next door.

Donna came to the clinic the previous week - for emergency contraception - after a condom split in her first experience of intercourse. She has now returned to talk to the doctor again.

“You feel really relaxed here,” she said. “I’m still young and I’m experiencing sexual relations for the first time. It’s nice to go to someone who knows the social side as well as the medical side.”

Dr Liz Stephens, based at the community gynaecology department of the Royal Free Hospital in Hampstead, is 28 and could pass for one of the students. Her youth is part of the clinic’s attraction, for Donna. “She can relate, and she’s quite funny,” she says.

Donna plans to study law after her A-levels. Some of her friends and relations are already mothers, however. “I know so many young girls that have had children, mostly when they’d just turned 16,” she says. “I don’t judge them. I just think it’s a shame because a lot of the girls are really intelligent and it seems a waste.”

The latest figures from the Office of National Statistics show slight rises in the conception rate among both under-16s and 15 to 19-year-olds. For younger teenagers (13-15), the conception rate is now 8.5 per 1,000 girls.

Brook Advisory Centres, who specialise in offering services to teenagers, are calling for concerted advertising of local services in schools and colleges to help to reduce teenage pregnancy.

School-based sex education is most effective at this when linked to access to contraceptive services, according to research this year from the NHS Centre for Reviews and Dissemination, based at the University of York.

But despite a huge expansion of services aimed at teenagers in the last 10 years, many are unaware of them. Brook’s research found that only 50 per cent of girls and 25 per cent of boys aged 14-15 know the location of their local centre. Schools are frightened to advertise such services, says Alison Hadley, of Brook. “A good lead from the Government on how best to publicise services for students would give schools a lot more confidence.”