Campaigners are making a fresh call for sex and relationships education (SRE) to become a compulsory subject in all state schools.
They suggested that statutory status would allow SRE to be treated the same as other subjects, with time allocated in school timetables to teaching and staff getting decent training.
A new small-scale survey of SRE teachers, conducted by the Sex Education Forum, found that over two-thirds (68%) said they needed more training to be able to teach good quality lessons in the subject.
And nine out of 10 (90%) said they should have been given the option to train as specialists in personal, social, health and economic (PSHE) education, of which sex and relationships was usually a part, during their initial teacher training.
The new It's My Right campaign is support by more than 30 organisations and chief executives, the Forum said.
The Forum's chair, Jane Lees, said: "For too long young people have been telling us about what they wish they had learnt in school about consent and relationships and how better knowledge of their body and sexual health facts could have kept them safer and healthier."
She said the Forum was calling for a commitment by all political parties to make SRE statutory.
"Standing up for statutory SRE is a move that political leaders can be proud of, and we know that young people, parents and teachers support it," Ms Lees said.
Daisy Ellis, acting policy director at the Terrence Higgins Trust, said: "We have reached a stage where teachers and students agree that the current approach to sex and relationships education is not working.
"Until those in Westminster make a solid commitment to make SRE a statutory part of the curriculum, generations of young people will continue to leave school unprepared and at risk of sexual ill health.
"In the 21st century, approaching sex education exclusively as a biology lesson just won't cut it.
"Young people need to be given an understanding of both sex and relationships, including the confidence to say no.
"If we want young people to make good decisions about sex, we need to give them the skills and encouragement to do so."
The new campaign comes in the wake of a number of reports warning that sex and relationships education is not up to scratch in many schools and growing fears that children are increasingly exposed to pornography, sexual images and sexual bullying, which could leave them open to exploitation and inappropriate behaviour.
A report published by Ofsted last year found that SRE needed to be improved in more than a third of schools and called f or secondary school pupils to learn more about issues such as pornography, relationships, sexuality and staying safe, rather than just the ''mechanics'' of reproduction.
SRE is compulsory in local authority-run state secondary schools, but campaigners argue that this only has to cover a narrow range of subjects and is not up to scratch.
A Department for Education spokesman said: "Sex and relationship education is compulsory in maintained secondary schools and it remains for primary schools to decide whether they want to teach it.
"All teaching of sex education must be age-appropriate and have regard to the Secretary of State's guidance.
"The criteria for teacher training is crystal clear that all trainees must be able to understand the needs of pupils and be able to engage and support them in order to meet the Teachers Standards and achieve Qualified Teacher Status (QTS).
"We have also funded the PSHE Association to produce case studies and help schools improve staff training, and in addition we have asked them to establish a new expert subject group to support teachers delivering sex and relationship education and PSHE."