Sex education may need to become more graphic because teenagers are increasingly experimenting with taboo practices, a new study has warned.

Researchers at the London School of Hygiene and Tropical Medicine (LSHTM) and University College London have been monitoring the changing sexual practices of youngsters since 1990.

They found that the number of 16-24s moving away from traditional sexual intercourse had doubled, with experts claiming that the easy access to internet pornography was partly behind the rise.

Dr Ruth Lewis, who conducted the work while at the LSHTM said: “At a time when much sex and relationships education is being updated, keeping pace with current trends in sexual practices is crucial so that curricula are tailored to the realities of young people's experiences.

"By shedding light on when some young people are having sex and what kinds of sex they are having, our study highlights the need for accurate sex and relationships education that provides opportunities to discuss consent and safety in relation to a range of sexual practices.”