Sex education should be compulsory in all primary and secondary schools to help protect children from abuse, a group of MPs said on Tuesday.
The Commons education select committee called for personal, social, health and economic education (PSHE) to be given statutory status and enough time devoted to the subject by properly trained teachers.
Sex and relationships education (SRE) should form a "core part" of these classes, they said, but recommended that parents retain the right to withdraw their children from lessons.
"Young people have a right to information that will keep them healthy and safe," said committee chairman Graham Stuart.
"SRE forms an important part of any school's efforts to safeguard young people from abuse, and is particularly needed to protect the most vulnerable children. PSHE builds character and resilience, and will help young people to live happy and healthy lives."
The report noted that PSHE in schools appears to have worsened despite efforts to reverse the trend.
An Ofsted report in 2013 said PSHE education required improvement or was inadequate in 40 percent of schools and pupils could be left ill-prepared for the physical and emotional changes of puberty.
The MPs' report warned: "There is a mismatch between the priority that the government claims it gives to PSHE and the steps it has taken to improve the quality of teaching in the subject."
The committee urged the Department for Education (DfE) to come up with a plan for introducing age-appropriate PSHE and SRE -- which should be renamed relationships and sex education (RSE) -- as statutory subjects in primary and secondary schools.
Currently it is not mandatory for primary schools to give sex and relationships lessons beyond what is covered in the science curriculum.
Local council-controlled secondaries have to provide SRE covering issues such as sexually transmitted diseases but academies are exempt from the rules.
A DfE spokeswoman said: "The government is working with schools and experts to ensure that young people are getting a decent education in PSHE and SRE."