Nearly a third of students have said that they were not taught about the legal age of consent for sex in schools, a survey has shown.

A study undertaken by the Sex Education Forum, part of the National Children’s Bureau, gave a worrying insight into the state of sex and relationship education in schools, revealing that less than half had learnt the difference between a good and a bad relationship.

Many of the respondents said that there had been a “complete absence” of discussion about real-life relationship issues and what they should do if something were to happen to them.

A total of 890 young people aged between 14 and 25 responded to the survey, with the majority aged between 16 and 17.

The research echoes findings in an Ofsted report released last year, which showed personal, social, health and economic (PSHE) education to be “inadequate” in 40 per cent of schools.

Lucy Emmerson, coordinator of the Sex Education Forum, said that the survey results showed the quality of sex education that children receive in England was a “lottery” and that knowing the age of consent was essential for healthy relationships.

“Learning about consent is integral to good quality sex and relationships education and every school should have a planned programme that includes content on bodily boundaries, gender and power, caring for one another, feelings and emotions and how to get help and advice,” Ms Emmerson said. “We need to listen to the evidence and make high-quality sex and relationships education a guarantee across all schools.”

Classroom union the Association for Teachers and Lecturers said that the study showed the “dire” need for young people to receive good sex and relationships education.

“It also highlights the need for education professionals to have high quality training and for sex and relationship teaching to be covered in a meaningful way and not just appear sporadically on the timetable,” ATL general secretary Mary Bousted said.