Three-quarters of young people are not taught about sexual consent, while one in seven said they did not receive any sex and relationship education (SRE) at all, and 95% said they were not taught about LGBT relationships, according to a report from the Terrence Higgins Trust.

The survey of young people by the HIV and sexual health charity said infrequent and poor-quality sex and relationship education in schools was creating a “safeguarding crisis” for young people.

The findings are in line with an Ofsted report in 2013, which found that SRE teaching was inadequate or required improvement in 40% of schools.

Where SRE is taught, Tuesday’s report found, young people said it was usually limited to biological topics such as reproduction, body parts and heterosexual sex.

The survey, called Shh … No Talking warned that SRE is “unfit” for the smartphone generation, leaving them vulnerable to abuse, bullying and poor mental and sexual health.

Ian Green, the chief executive of the Terrence Higgins Trust, said: “In this report, we’ve seen the stark reality of SRE in this country and heard saddening stories of how one generation of young people have been exposed to low self-esteem, homophobia, bullying, unhealthy relationships and poor sexual health as a result of the lack of quality SRE in our schools.

“The government’s quiet blocking of compulsory SRE will condemn another generation of young people to leave school armed with little to no information on issues like LGBT relationships, gender identity and consent.

“Without trusted information from schools on anything other than the biological basics of heterosexual sex, young people will turn to less reliable sources such as the internet or their peers as they navigate life outside the classroom.”

In February, the government refused to make SRE compulsory, against the advice of parents, educators, the education select committee and young people themselves. The women and equalities select committee, which is looking into how to tackle sexual violence, harassment and bullying in schools, has found overwhelming support for SRE and personal, social and health education (PSHE) to be made mandatory in schools.

Other findings in the charity’s report include:

• Half of more than 900 respondents aged 16-24 rated the SRE they had received as “poor” or “terrible”.
• Just 10% of respondents rated it “excellent” and 2% rated it “good.”
• Just 5% of young people who said they received SRE were taught about LGBT sex and relationships, while 97% believed it should be LGBT-inclusive.
• About 97% of those who said they received SRE did not recall gender identity being taught and 89% were not taught about sex and pleasure.
• 61% said they received SRE just once a year or less.
• 32% of respondents did not remember receiving any information on HIV in schools, while 27% said they did not receive any information on HIV.
• 99% of young people surveyed thought SRE should be mandatory in schools.

At the moment, SRE is only mandatory in state-maintained secondary schools, which account for 40% of all schools. Academies, primary schools, free schools and private schools are not obliged to teach it.

Green said it was “shocking” that Department for Education guidance on SRE had not been updated for 16 years.

“Young people are getting information about sex and relationships in a world before social media existed, before smartphones, before equal marriage or civil partnerships,” said Green. “It is wholly unfit to prepare them for the realities of sex and relationships in 2016.”

Paul Bishop, an assistant headteacher and director of sixth form at Saint Cecilia’s school in Wandsworth, south-west London, said: “It seems everyone thinks SRE is someone else’s job. The result is an information vacuum which leaves children and young people reliant on inaccurate or unrealistic depictions of sex and relationships from alternative sources, such as their peer groups and social networks.”

Lauren Alexandra Young, 18, who took part in the survey, said: “My SRE consisted of watching a cartoon video of a heterosexual couple, labelling the male anatomy and learning how pregnancies occur. We weren’t taught about sexual intercourse, other contraception, health relationships or even periods.

“Many young people struggle with their feelings of sexuality and gender and if no one is talking to them about it, or allowing them to discuss it openly, they will internalise their worry and it will grow into something ugly and harmful for the individual.”

A total of 914 young people aged 16-25 completed the survey, which was online for seven weeks in February.

A Department for Education spokesperson said: “High quality sex and relationship education (SRE) is a vital part of preparing young people for life in modern Britain - helping them make informed choices, stay safe and learn to respect themselves and others. Our guidance is clear that young people, whatever their sexuality, need to feel that sex and relationships education is relevant to them and sensitive to their needs.

“We also expect all school to deliver PSHE to a high standard. We know that the vast majority of schools and teachers recognise the importance of PSHE, and trust teachers to tailor their lessons to best suit their pupils. We are focusing on raising the quality of PSHE teaching and working with leading headteachers and practitioners to look at how best to achieve this.”